Co-reporter:Mengmeng Chen, Xiaolei Ma, Rui Ma, Zhe Wen, Fei Yan, Kai Cui, Hong Chen, and Yongdan Li
Industrial & Engineering Chemistry Research November 29, 2017 Volume 56(Issue 47) pp:14025-14025
Publication Date(Web):November 7, 2017
DOI:10.1021/acs.iecr.7b03585
A reduction-modified MoO3 catalyst is employed in the ethanolysis of Kraft lignin in supercritical ethanol. The reduction pretreatment under hydrogen atmosphere is carried out and shows a strong effect on the activity. A sample MoO3@623 K, that is, pretreated at 623 K, achieves the highest overall yield of small molecules, 1266 mg/g lignin. Compared with that using untreated MoO3 sample, the yield increases almost 15%, implying that the reduction pretreatment is effective for the enhancement of product yields and a promising strategy for industrial application. The XRD patterns and XPS spectra indicate that a transformation of bulk MoO3 to MoO2 happens at around 773 K, therefore, a MoO3@773 K catalyst gives a very low yield. The oxygen vacancies and Mo6+ together with Mo5+ formed during the partial reduction facilitate the formation of active species.
Co-reporter:Jihui Wang, Huawang Zhao, Gary Haller, Yongdan Li
Applied Catalysis B: Environmental 2017 Volume 202(Volume 202) pp:
Publication Date(Web):1 March 2017
DOI:10.1016/j.apcatb.2016.09.024
•Cu-CHA catalyst marks a great breakthrough in NH3-SCR area due to excellent hydrothermal stability.•The state of Cu in the reaction was introduced.•The preparation methods were compared and the reaction mechanism was outlined.•The comparison between Cu-SSZ-13 and Cu-SAPO-34 catalysts was made.The development of Cu-chabazite (CHA) catalysts, i.e. Cu-SSZ-13 and Cu-SAPO-34, represents a significant technology breakthrough for the removal of NOx by selective catalytic reduction (SCR) with ammonia. Cu-CHA catalysts show an excellent hydrothermal stability towards high temperature aging and wide active temperature windows for the ammonia SCR reaction. This work summarizes the recent progress in the development of the Cu-CHA catalysts for the NH3-SCR reaction. The state of Cu in the reaction and the preparation methods on the catalytic performance are discussed. The advances in the understanding of the reaction mechanism are reviewed. The hydrothermal stability of the typical Cu-CHA catalysts are compared.Download high-res image (136KB)Download full-size image
Co-reporter:Yicheng Zhao, Bin Zhu, Peter Lund, Angelo Basile, Yongdan Li
International Journal of Hydrogen Energy 2017 Volume 42, Issue 27(Volume 42, Issue 27) pp:
Publication Date(Web):6 July 2017
DOI:10.1016/j.ijhydene.2017.06.168
Co-reporter:Xueqi Xing, Yongjie Huo, Xiang Wang, Yicheng Zhao, Yongdan Li
International Journal of Hydrogen Energy 2017 Volume 42, Issue 27(Volume 42, Issue 27) pp:
Publication Date(Web):6 July 2017
DOI:10.1016/j.ijhydene.2017.03.034
•A promising electroactive species benzophenone (BP) is used as the anolyte.•BP exhibits a superior electrochemical properties and a high solubility.•A flow battery is achieved with a theoretical energy density of 139 Wh L−1.A new electroactive species benzophenone (BP) is identified for the anolyte of an all-organic redox flow battery (AORFB) due to its low redox potential, high electrochemical reversibility and stability, and high solubility in non-aqueous electrolyte. BP also shows high stability in a wide temperature range, and the elevated temperature enhances the redox reactions and the mass transfer rates, leading to an exponential increase of the diffusion coefficient. An AORFB based on BP anolyte is achieved with a cell voltage of 2.41 V and a theoretical energy density of 139 Wh L−1. The cycling performance shows a stable coulombic efficiency of 81%. The results presented indicate that organic molecule BP is a promising anolyte active species for high-energy density AORFBs.Download high-res image (146KB)Download full-size image
Co-reporter:Jingjing Shao, Guangming Zeng, Yongdan Li
International Journal of Hydrogen Energy 2017 Volume 42, Issue 27(Volume 42, Issue 27) pp:
Publication Date(Web):6 July 2017
DOI:10.1016/j.ijhydene.2017.04.066
•Zn-doped LaNi1−xZnxO3−δ perovskite structured oxides are obtained.•There exists a limit for zinc substitution in LaNi1−xZnxO3−δ.•Highly dispersed active metal and ZnO form on La2O3 surface during reduction.•Zn substitution in LaNi1−xZnxO3−δ suppresses coking and sintering.A LaNi1−xZnxO3−δ perovskite structured oxide catalyst is prepared with a one-step citrate complex method and applied as the precursor of the catalyst in ethanol steam reforming (ESR) reaction. The Zn substitution makes the perovskite-oxide difficult to be reduced due to the strong bond of La–O–Zn, which favors the formation of small Ni particle size thus moderates the sintering of nickel. The doping of Zn also effectively suppresses coking in the reaction. The spillover of oxygen and the electron donation effect of Zn species to the surface of metallic nickel is confirmed with an XPS technique. The doping amount shows an optimum value and a LaNi0.85Zn0.15O3−δ sample exhibits the highest H2 product yield and best stability at 700 °C.Download high-res image (175KB)Download full-size image
Co-reporter:Tianmu Lv, Jiang Li, Xiao Dong, Ji Yu, ... Yongdan Li
International Journal of Hydrogen Energy 2017 Volume 42, Issue 27(Volume 42, Issue 27) pp:
Publication Date(Web):6 July 2017
DOI:10.1016/j.ijhydene.2017.02.114
•Anode supported SOFC with thin film SDC as electrolyte was tested.•A linear discharge model is derived to simulate the I–V curve of the cell.•A reasonable explanation for the linearity of the I–V curve is given.In this work, a solid oxide fuel cell with 60 μm samarium doped ceria film as the electrolyte is fabricated with a co-pressing technique. The performance of the cell is measured at 600, 650 and 700 °C. The corresponding maximum power outputs are 236, 331 and 401 mW cm−2, respectively. The measured current–voltage (I–V) curves are straight lines. A linear discharge model is derived based on the Gorelov and Liu modified electromotive force (EMF) equations. The model fits the measured I–V curves with the maximum errors less than 1.5%. The overall activation overpotential of the cell is therefore postulated to be proportional to the polarization current.Download high-res image (256KB)Download full-size image
Co-reporter:Jiang Li, Tianmu Lv, Xiao Dong, Ji Yu, ... Yongdan Li
International Journal of Hydrogen Energy 2017 Volume 42, Issue 27(Volume 42, Issue 27) pp:
Publication Date(Web):6 July 2017
DOI:10.1016/j.ijhydene.2017.02.106
•Internal electronic resistance of the SOFC is determined with different methods.•Power losses of the SOFC are discussed.•Overall efficiency of the SOFC is evaluated and discussed.Samarium doped ceria (SDC) shows obvious electronic conduction in a reducing atmosphere, which results in internal short-circuiting of the SOFC. In this work, we initiatively combine the Gorelov modified electromotive force (EMF) method and the Liu modified EMF method to determine the internal electronic resistance of the SOFC with 60 μm SDC film electrolyte. The internal electronic resistance determined with the Gorelov modified EMF method is a little larger than that determined with the Liu modified EMF method. The power loss of the SOFC is mainly resulted from the internal short-circuiting, oxygen ionic resistance and electrode polarization resistance. At low external current density, the internal short-circuiting power loss is predominant, while at high current density the oxygen ionic resistance power loss is predominant. Temperature has little effect on the maximum efficiency of the SOFC. When the SOFC works at the maximum power output, the efficiency of the cell is about 30%, but if the electronic conduction of the SDC electrolyte could be eliminated, the efficiency could be improved by 2.5 times.Download high-res image (226KB)Download full-size image
Co-reporter:Jingran Xiao, Huali Huang, Qiuyang Huang, Xiang Li, Xuelan Hou, Le Zhao, Rui Ma, Hong Chen, Yongdan Li
Applied Catalysis B: Environmental 2017 Volume 212(Volume 212) pp:
Publication Date(Web):5 September 2017
DOI:10.1016/j.apcatb.2017.04.075
•A FeCoW/Fe2O3 composite anode gives 1.18 mA/cm2 photocurrent at 1.23 V vs. RHE.•The Von is 0.67 V vs. RHE with 170 mV cathodic shift from 0.85 V of Fe2O3.•The applied bias photon–to–current efficiency is 2.7 times that of Fe2O3.•The FeCoW/Fe2O3 photoanode has a low bias photoresponse as 0.3 V vs. RHE.•The composite exhibits very good photostability.A FeCoW oxy–hydroxide gel coated Fe2O3 film photoanode has been examined for photoelectrochemical (PEC) water oxidation reaction. The FeCoW coating acts as a hole storage layer, resulting in efficient hole extraction from Fe2O3 for water oxidation. In addition, the surface state of FeCoW/Fe2O3 shifts to higher position, thus allows for a lower turn–on voltage (Von) of the photocurrent. The composite anode exhibits an 84% increase of the photocurrent, at 1.23 V versus reversible hydrogen electrode (RHE), over the bare Fe2O3 photoanode. The Von is as low as 0.67 V vs. RHE. The applied bias photon–to–current efficiency of the composite is 2.7 times higher than that of the bare Fe2O3. Moreover, an extremely low bias photoresponse of 0.45 V vs. RHE and a good stability are observed with the FeCoW/Fe2O3 photoanode. Besides, with changing of the thickness of the FeCoW coating slurry, the PEC performance of the FeCoW/Fe2O3 photoanode can be tuned.Download high-res image (97KB)Download full-size image
Co-reporter:Le Yang, K. Seshan, Yongdan Li
Catalysis Today 2017 Volume 298(Volume 298) pp:
Publication Date(Web):1 December 2017
DOI:10.1016/j.cattod.2016.11.030
•Overview of research on lignin monomers.•Overview of research on lignin dimers.•Numerous examples utilizing homogenous catalysts and heterogeneous catalysts.•Selective cleavage of CO and CC bonds.Biomass-based energy fulfills the future need of sustainable humanity. The utilization of lignin which is a primary constituent of biomass still remains the world most difficult problem due to its highly aromatic polymeric structure. Investigations on lignin model compounds renew the knowledge on CC and CO bond cleavage chemistry and indicate directions for lignin deconstruction. This review is to present the state of the art of the chemical transformation of lignin model compounds including monomers and dimers based on catalyst classifications, with emphasis on the fundamental catalytic chemistry in different processes. Moreover, how ideas derived from concepts transform to strategies for controlling the reaction pathways is also discussed.Download high-res image (90KB)Download full-size image
Co-reporter:Huawang Zhao, Huisheng Li, Xianghui Li, Mengke Liu, Yongdan Li
Catalysis Today 2017 Volume 297(Volume 297) pp:
Publication Date(Web):15 November 2017
DOI:10.1016/j.cattod.2017.05.060
•1 wt.% Fe loaded Cu-SAPO-34 shows enhanced SCR performance above 200 °C.•1 wt.% Fe loading by impregnation method produces more isolated Cu2+ ions.•The addition of 1 wt.% Fe decreases the amount of surface bulk CuO species.•The addition of 1 wt.% Fe suppresses the NH3 oxidation activity.•The isolated Fe3+ ions in Cu-SAPO-34 sample are additional active sites.A number of Fe loaded Cu-SAPO-34 (Fe: Cu-SAPO–34 = 0.5, 1 and 1.5 wt.%) catalysts were prepared with incipient wetness impregnation of iron acetate solution on a one-pot synthesized Cu-SAPO-34 sample. The Fe/Cu-SAPO-34 sample with 1 wt.% Fe loading shows the best selective catalytic reduction performance among the samples tested at temperatures above 200 °C. The results of ultraviolet-visible diffuse reflectance spectroscopy indicate that isolated Fe3+ ions, FexOy oligomers, and Fe2O3 particles coexist in the Fe incorporated samples. Further examinations tell that the bulk CuO on the surface in the Cu-SAPO-34 sample with appropriate amount of Fe addition transforms to isolated Cu2+ ions, which enhances its catalytic activity in the temperature range of 200–350 °C. The Fe: Cu-SAPO–34 = 1 wt.% sample exhibits a lower NH3 oxidation ability at high temperatures than that of Cu-SAPO-34, which is due to the reduced amount of bulk CuO species on the surface. Both the reduced NH3 oxidation ability and the additional isolated Fe3+ sites contribute to the excellent activity of the Fe: Cu-SAPO-34 = 1 wt.% sample above 350 °C.Download high-res image (135KB)Download full-size image
Co-reporter:Fei Yan, Rui Ma, Xiaolei Ma, Kai Cui, Kai Wu, Mengmeng Chen, Yongdan Li
Applied Catalysis B: Environmental 2017 Volume 202(Volume 202) pp:
Publication Date(Web):1 March 2017
DOI:10.1016/j.apcatb.2016.09.030
•A MoC1-x/Cu-MgAlOz catalyst is employed in lignin conversion.•The products include alcohols, esters, and aromatic compounds.•Aromatic compounds are achieved in a high yield.•High temperature favors the conversion of Kraft lignin.•The catalyst can be reused for at least 4 runs.The complete conversion of Kraft lignin is examined over a MoC1-x/Cu-MgAlOz catalyst in pure ethanol to give value-added chemicals with small molecular weight, including C6 alcohols, C8C10 esters, benzyl alcohols and arenes, without the formation of char or tar. MoC1-x/Cu-MgAlOz exhibited much higher activity than the previously reported MoC1-x/AC, CuMgAlOy and Cu-MgAlOz catalysts and achieved the highest yield of aromatic compounds, 575 mg/g lignin, at 330 °C. The complete cleavage of aryl-O bonds in phenols is observed at temperatures over 300 °C. Furthermore, the MoC1-x/Cu-MgAlOz catalyst is reusable with a 22.4% loss in the yield of aromatic compounds after 5 cyclic runs.Download high-res image (123KB)Download full-size image
Co-reporter:Jingran Xiao, Huali Huang, Qiuyang Huang, Le Zhao, Xiang Li, Xuelan Hou, Hong Chen, Yongdan Li
Journal of Catalysis 2017 Volume 350(Volume 350) pp:
Publication Date(Web):1 June 2017
DOI:10.1016/j.jcat.2017.02.001
•The rapidly cooled hematite photoanode displays a sharp increase of photocurrent.•The sample shows decreased diameter and reduced surface disorders.•Fe3+ partial reduction and absorbed OH group amount decrease are observed.•Both the bulk and surface electron–hole recombination rate are suppressed.•Slow cooling or rapid heating treatment shows converse effect.The preparation of hematite photoanodes for photoelectrochemical water splitting reactions always involves a high-temperature annealing process. The cooling rate during the annealing process is discovered as an important factor deciding the anode performance. Rapid cooling of the hematite photoanode increased the photocurrent from 0.635 mA cm−2 for the normally cooled sample to 0.856 mA cm−2 at 1.23 V vs. RHE. The rapidly cooled hematite nanowires showed decreased diameter, reduced surface disorder, Fe partial reduction, and decreased number of surface OH groups simultaneously with a red shift of light absorption. Both the charge separation and injection efficiencies are improved, confirming the simultaneous decrease of the bulk and surface electron–hole recombination rates. The bulk electron–hole recombination rate depends on the diameter of the nanowires, while the surface electron–hole recombination rate is lowered due to the reduced surface trap states. The photocurrent measurement results with H2O2 as the sacrificial agent indicate that the suppression of surface recombination is more important than that of bulk recombination. In contrast, slow cooling or rapid heating exhibits a negative effect on the performance of the hematite photoanode.Download high-res image (115KB)Download full-size image
Co-reporter:Nianjun Hou, Ping Li, Tianmu Lv, Tongtong Yao, Xueli Yao, Tian Gan, Lijun Fan, Pengzhi Mao, Yicheng Zhao, Yongdan Li
Catalysis Today 2017 Volume 298(Volume 298) pp:
Publication Date(Web):1 December 2017
DOI:10.1016/j.cattod.2017.06.034
•Sm0.5Ba0.5MnO3 is studied as an anode of solid oxide fuel cells fed with methanol.•The single cell exhibits a maximum power density of 415 mW cm−2 at 850 °C.•The cell shows a promising stability under both low and high current densities.Sm0.5Ba0.5MnO3-δ (SBMO) has been synthesized with the Pechini method and investigated as an anode material of solid oxide fuel cells with H2 and methanol as fuels. A cubic perovskite structure is formed after reduction. The reduction process of SBMO is studied with X-ray photoelectron spectroscopy and temperature programmed reduction techniques. The electrical conductivities of an SBMO sample sintered at 950 °C are 1.15 and 0.10 S cm−1 at 850 °C in air and H2, respectively. A single cell with an SBMO anode layer and a 300-μm La0.8Sr0.2Ga0.8Mg0.2O3-δ electrolyte layer exhibits a maximum power density (Pmax) of about 150 mW cm−2 at 850 °C with H2 as fuel. The electrical conductivity of the anode layer with methanol as fuel is improved by the moderate carbon deposition, and the Pmax increases to about 415 mW cm−2. The cell fed with methanol also shows a promising stability.Download high-res image (186KB)Download full-size image
Co-reporter:Mengmeng Chen, Wenyue Hao, Rui Ma, Xiaolei Ma, Le Yang, Fei Yan, Kai Cui, Hong Chen, Yongdan Li
Catalysis Today 2017 Volume 298(Volume 298) pp:
Publication Date(Web):1 December 2017
DOI:10.1016/j.cattod.2017.08.012
•An alumina supported molybdenum nitride catalyst for lignin ethanolysis.•The products are alcohols, esters, mono-phenols, benzyl alcohols and arenes.•The preparation and reaction conditions have great influences on the activity.•907 mg/g lignin aliphatics and 282 mg/g lignin aromatics are obtained.•No significant activity loss is observed in three runs.An alumina supported molybdenum nitride catalyst (Mo2N/Al2O3) is examined for the ethanolysis of Kraft lignin in supercritical ethanol in a batch reactor with an initial nitrogen pressure of 0 MPa (gauge). No char or tar is formed in this process. The Mo loading as well as the nitriding temperature in the catalyst preparation process has a great influence on the activity. The best performance is obtained over 30 wt% Mo2N/Al2O3 catalyst nitrided at 700 °C. The overall yields of sulfur-free small-molecular products achieve the maximum value of 1189 mg/g lignin, with aliphatic compounds accounting for 907 mg/g lignin and aromatic compounds 282 mg/g lignin, respectively. Both the product yields and the molecular distribution are also strongly dependent on the reaction time and temperature. Furthermore, the Mo2N/Al2O3 catalyst exhibits an excellent recycle performance with no significant activity loss after at least three runs. After reaction, the bulk structure of Mo2N/Al2O3 catalyst was well-preserved only with a slight surface oxidation.Download high-res image (122KB)Download full-size image
Co-reporter:Kai Cui, Le Yang, Zewei Ma, Fei Yan, Kai Wu, Yushuai Sang, Hong Chen, Yongdan Li
Applied Catalysis B: Environmental 2017 Volume 219(Volume 219) pp:
Publication Date(Web):15 December 2017
DOI:10.1016/j.apcatb.2017.08.009
•Guaiacol is converted to alkylphenols in supercritical ethanol over MoO3.•The conversion of guaiacol and the selectivity of alkylphenols are high.•Novel reaction pathways of deoxygenation and substitutions are proposed.•A MoOxCyHz active species developed from alcohol system is verified.•Reasons of different activities in alcohols and deactivation are revealed.Selective conversion of guaiacol over MoO3 to produce various alkylphenols, including ethylphenols, isopropylphenols, butylphenols (tert-, sec-) and tert-amylphenol is investigated in ethanol without the addition of gaseous hydrogen. A high conversion of 99% is achieved at 280 °C for 4 h and the total alkylphenols account for up to 94% in the quantified products. Six molecules, i.e. 2,5-diethylphenol, 2,6-diisopropylphenol, 2,4-diisopropylphenol, 2,6-ditertbutylphenol, 2,4-ditertbutylphenol and 2,6-ditertbutyl-4-ethylphenol, are the main outcomes. The higher alkylphenols in the aforesaid products are verified to form via a novel reaction step in which hydrogen atom at the α-carbon of the lower alkylphenol is substituted consecutively with methyl or ethyl groups. Further examination reveals that catechol is formed as the intermediate via demethylation of guaiacol and followed by direct conversion to low alkylphenols without the formation of phenol. Post-catalytic analysis indicates that an oxycarbohydride phase (MoOxCyHz) with Mo5+ developed in the supercritical alcohol batch system played the role of active species. Ethanol is found to be the most effective solvent for the conversion. The MoO3 catalyst undergoes a gradual deactivation resulted from the consumption of Mo5+ and carbon deposition but can be regenerated with a simple calcination.Download high-res image (209KB)Download full-size image
Co-reporter:Xueli Yao, Ping Li, Baolong Yu, Fei Yang, ... Yongdan Li
International Journal of Hydrogen Energy 2017 Volume 42, Issue 34(Volume 42, Issue 34) pp:
Publication Date(Web):24 August 2017
DOI:10.1016/j.ijhydene.2017.02.008
•NiO-Ce0.8Sm0.2O1.9 composite anode is synthesized with a hydrothermal technique.•Sufficient sintering of the anode leads to high electrical conductivity.•The hydrothermally synthesized anode possesses a high catalytic activity.•The single cell exhibits a maximum power density of 738 mW cm−2 at 700 °C.•The single cell possesses promising stability with methanol as fuel.NiO-Ce0.8Sm0.2O1.9 (Ni-SDC) composite anode powders are synthesized with a hydrothermal technique. The average size of the particles in the anode powder is about 10 nm. Different phases distribute uniformly in the composite. The anode sintered at 700 °C exhibits an electrical conductivity of above 100 S cm−1, three orders of magnitude higher than that of a similar solid-mixed composite anode with the same composition. The anode synthesized through the hydrothermal process also possesses a higher catalytic activity. An SDC-carbonate composite electrolyte-supported single cell with the composite anode exhibits a maximum power density of 738 mW cm−2 at 700 °C with H2 as fuel, much higher than that of a similar cell with a solid-mixed anode. The cell also exhibits a promising stability with methanol as fuel.Download high-res image (230KB)Download full-size image
Co-reporter:Baolong Yu, Yicheng Zhao, Yongdan Li
Journal of Power Sources 2016 Volume 306() pp:387-393
Publication Date(Web):29 February 2016
DOI:10.1016/j.jpowsour.2015.12.043
•SnO2/SDC is introduced as an extra anode layer in a direct carbon fuel cell.•The fuel cell is tested under the fuel mode.•The fuel cell achieves the highest output of 192 mW cm−2 at 750 °C.•SnO2 is reduced by carbon under the fuel mode.•The resistance of the cell remains almost unchanged after discharge.The role of a SnO2-samarium doped ceria (SDC) additional anode layer in a direct carbon fuel cell (DCFC) with SDC-(Li0.67Na0.33)2CO3 composite electrolyte and lithiated NiO-SDC-(Li0.67Na0.33)2CO3 composite cathode is investigated and compared with a NiO-SDC extra anode layer. Catalytic grown carbon fiber mixed with (Li0.67Na0.33)2CO3 is used as a fuel. At 750 °C, the maximum power outputs of 192 and 143 mW cm−2 are obtained by the cells with SnO2-SDC and NiO-SDC layers, respectively. In the SnO2-SDC layer, the reduction of SnO2 and the oxidation of Sn happen simultaneously during the cell operation, and the Sn/SnO2 redox cycle provides an additional route for fuel conversion. The formation of an insulating dense interlayer between the anode and electrolyte layers, which usually happens in DCFCs with metal anodes, is avoided in the cell with the SnO2-SDC layer, and the stability of the cell is improved consequently.
Co-reporter:Jingran Xiao, Xuelan Hou, Le Zhao, Yongdan Li
International Journal of Hydrogen Energy 2016 Volume 41(Issue 33) pp:14596-14604
Publication Date(Web):7 September 2016
DOI:10.1016/j.ijhydene.2016.06.151
•ZnO:Ga/ZnO core-shell array is prepared with a two-step hydrothermal method.•ZnO:Ga/ZnO junction with nearly the same lattice structure is obtained.•The ZnO:Ga/ZnO composite exhibits visible light absorption and improved conductivity.•The ZnO:Ga/ZnO photoanode exhibits remarkably enhanced PEC performance.•The ZnO:Ga/ZnO composite shows better photostability both in neutral and alkaline electrolyte.We report a ZnO:Ga/ZnO isostructural nanojunction photoanode with core-shell structure for photoelectrochemical water splitting. Ga-doped zinc oxide (ZnO:Ga) shell is grown in situ on the vertically aligned ZnO array core in a hydrothermal process. The as-prepared ZnO:Ga/ZnO composite with nearly the same lattice structure in the two phases exhibits enhanced light absorption and improved electrical conductivity. The photocurrent density of the composite achieves 0.6 mA cm−2 under AM 1.5G simulated light irradiation with an applied bias of 1.23 vs. Ag/AgCl, which is three times higher than that of the anode made of pristine ZnO array. Under visible light (λ > 420 nm) irradiation, the current density reaches 0.06 mA cm−2 at the same condition. Moreover, the ZnO:Ga/ZnO composite shows better photostability than ZnO both in neutral and alkaline electrolyte. The isostructural nanojunction with excellent lattice match is thus demonstrated to be a promising material as the photoanode in water splitting.
Co-reporter:Xiaolei Ma, Rui Ma, Wenyue Hao, Mengmeng Chen, Fei Yan, Kai Cui, Ye Tian, and Yongdan Li
ACS Catalysis 2015 Volume 5(Issue 8) pp:4803
Publication Date(Web):July 7, 2015
DOI:10.1021/acscatal.5b01159
One-pot complete catalytic ethanolysis of Kraft lignin into C6–C10 chemicals, that is, aliphatic alcohols, esters, phenols, benzyl alcohols, and arenes, is achieved with a batch reactor over a number of supported molybdenum-based catalysts at 553 K in pure ethanol under autogenous pressure of 10.6 MPa. Metallic molybdenum, its carbide, and nitride all show remarkable activity, with the carbide and metallic catalysts giving the higher overall yields: 1640 and 1390 mg/g lignin, respectively. The major phases composing the catalysts are well-preserved after the reaction; however, the detection of Mo(V) species verifies the partial oxidation of molybdenum, which leads to the formation of the dissociative Mo species, such as molybdenum V ethoxide, in the fluid phase. Through the product analysis and catalyst characterization, the common route of lignin conversion to value added chemicals over the Mo-based catalyst is presented in detail. Kraft lignin is first fragmented into segments with m/z ∼ 700–1400 via a noncatalytic ethanolysis process. Meanwhile, the main active Mo(V) species dissociate from the solid catalyst into the fluid due to the interaction of ethanol. Then mainly the dissociative species catalyze, with the participation of the radicals, the further degradation of the segments into small molecules.Keywords: chemicals; depolymerization; heterogeneous catalysis; lignin; molybdenum; supercritical ethanol
Co-reporter:Rui Ma, Kai Cui, Le Yang, Xiaolei Ma and Yongdan Li
Chemical Communications 2015 vol. 51(Issue 51) pp:10299-10301
Publication Date(Web):14 May 2015
DOI:10.1039/C5CC01900A
An activated carbon supported α-molybdenum carbide catalyst (α-MoC1−x/AC) showed remarkable activity in the selective deoxygenation of guaiacol to substituted mono-phenols in low carbon number alcohol solvents. Combined selectivities of up to 85% for phenol and alkylphenols were obtained at 340 °C for α-MoC1−x/AC at 87% conversion in supercritical ethanol. The reaction occurs via consecutive demethylation followed by a dehydroxylation route instead of a direct demethoxygenation pathway.
Co-reporter:Yang Li, Xiaoli Zhang, Shaohong Jiang, Haitao Dai, Xiaowei Sun, Yongdan Li
Solar Energy Materials and Solar Cells 2015 Volume 132() pp:40-46
Publication Date(Web):January 2015
DOI:10.1016/j.solmat.2014.08.015
•Polygonal ZnO nanorod photoelectrode was coated with CdS and NiO layers.•NiO/CdS@ZnO electrode shows high activity and stability under simulated sunlight.•NiO/CdS@ZnO photoanode is able to fulfill overall water splitting without bias.•NiO thin layers act as efficient cocatalysts, and protect CdS from photocorrosion.•The small diameters of the ZnO nanorods reduce the e−/h+ recombination.Polygonal ZnO nanorods are synthesized with a hydrothermal technique and coated with an ultrathin CdS layer. A NiO cocatalyst layer is then deposited on the surface of the CdS coated ZnO and makes up a three-component nanostructured composite photoelectrode (NiO/CdS@ZnO). This composite photoelectrode shows an improved photoelectrochemical performance under Air Mass 1.5 (AM 1.5) simulated sunlight. It generates a photocurrent density of 950 µA/cm2 with a comparatively low potential −0.6 V vs. Ag/AgCl in a 0.5 M Na2S and Na2SO3 solution, which is 6.78 times as much as that of the as-grown ZnO nanorods. Furthermore, it is also an efficient photoanode to split pure water, producing a photocurrent density of 530 µA/cm2 at 0.5 V vs. Ag/AgCl in a 1 M Na2SO4 solution. In the composite, ZnO nanorods absorb UV light with a wide band gap, 3.2 eV, while CdS, with a narrow band gap (2.4 eV), utilizes the remaining visible light, furthermore, an ordered transfer of the charge carriers occurs in the component phases. The photoluminescence (PL) experiment results prove that the direct loading of NiO on ZnO results in an inactive material. However, both the CdS/ZnO and NiO/CdS@ZnO composites are active and the charge carrier separations in them are effectively improved than in the as-grown ZnO.
Co-reporter:Jingran Xiao, Xiaoli Zhang, Yongdan Li
International Journal of Hydrogen Energy 2015 Volume 40(Issue 30) pp:9080-9087
Publication Date(Web):10 August 2015
DOI:10.1016/j.ijhydene.2015.05.122
•The C3N4/Pt/ZnO photoanode exhibits remarkably enhanced PEC performance.•The C3N4/Pt/ZnO photoanode achieves visible light response.•ZnO nanowires are prepared with a hydrothermal technique.•g-C3N4 nanosheets are coated on the surface of ZnO nanowires by spin-coating.•Pt nanoclusters locate at the interface between ZnO and g-C3N4.In this work, graphite-like C3N4 (g-C3N4) is deposited on the surface of ZnO nanowires (NWs) and a nanocomposite g-C3N4/ZnO photoanode is made for the photoelectrochemical (PEC) water splitting under air mass 1.5 (AM 1.5) simulated sunlight illumination. Pt nanoclusters are further incorporated at the g-C3N4/ZnO interface and a tricomponent C3N4/Pt/ZnO photoanode is adapted. Both g-C3N4 and ZnO act as the light absorber to create electron hole pairs, while the Pt nanoclusters serve as the cocatalyst to facilitate the transfer of the photogenerated electrons. The g-C3N4/Pt/ZnO photoanode generates a photocurrent density of 120 μA cm−2 at 0.5 V vs. Ag/AgCl in a 0.5 M Na2SO4 solution, which is 9 times higher than that of the anode made of ZnO and 4.5 times higher than that of the g-C3N4/ZnO anode. Furthermore, with the visible light absorption of g-C3N4, the g-C3N4/Pt/ZnO photoanode gives a photocurrent density of 32 μA cm−2 at 0.5 V vs. Ag/AgCl under visible light (λ > 420 nm) illumination.
Co-reporter:Ping Li, Yicheng Zhao, Baolong Yu, Jiang Li, Yongdan Li
International Journal of Hydrogen Energy 2015 Volume 40(Issue 31) pp:9783-9789
Publication Date(Web):17 August 2015
DOI:10.1016/j.ijhydene.2015.06.026
•La2Ni0.9Fe0.1O4 is investigated as an anode material of a solid oxide fuel cell.•The electrical conductivity of the anode is improved by carbon deposition.•The effects of the carbon source on the conductivity of the anode are studied.•The single cell exhibits a maximum power density of 166 mW cm−2 at 800 °C.La2Ni0.9Fe0.1O4+δ (LNF) with a K2NiF4-type structure is synthesized with a citrate complexing method and used as an anode material of a solid oxide fuel cell. It is reduced to La2O3 and Ni–Fe alloy phases in H2 atmosphere. The electrical conductivity of the anode material is enhanced by carbon deposition with CH4 and methanol as the carbon sources, respectively. The deposited carbon is characterized with a scanning electron microscope, a transmission electron microscope, thermogravimetric analysis and a Raman spectrometer. The carbon deposited from methanol has a higher degree of graphitization than that from CH4, bringing about a higher electrical conductivity. The conductivity of the reduced LNF at 800 °C increases from 0.23 S cm−1 to 2.47 S cm−1 after the carbon deposition in methanol. The increase of the anode conductivity results in an improvement of the fuel cell performance. A maximum power density of 166 mW cm−2 is obtained at 800 °C from a single cell with La0.8Sr0.2Ga0.83Mg0.17O3-δ as the electrolyte and Ba0.5Sr0.5Co0.8Fe0.2O3-δ as the cathode.
Co-reporter:Xuelan Hou, Shaohong Jiang, Yang Li, Jingran Xiao, Yongdan Li
International Journal of Hydrogen Energy 2015 Volume 40(Issue 45) pp:15448-15453
Publication Date(Web):7 December 2015
DOI:10.1016/j.ijhydene.2015.09.082
•A InN/GaZnON composited (oxy)nitride catalyst is synthesized.•Photocatalytic overall water splitting without extra cocatalyst is achieved.•The doping of Ni greatly improves visible light absorption.•The doping of Ni greatly improves the photocatalytic activity.A (oxy)nitride composite- InN/GaZnON- is synthesized and utilized as the photocatalyst for visible-light-driven overall water splitting. The effect of Ni doping on the performance of the composite photocatalyst is investigated. The X-ray diffraction pattern indicates that the catalyst is a composite material consisting of InN and GaZnON phases. Ni is doped into the crystal lattices of the two phases. Ni doped InN/GaZnON composite achieves overall water splitting even without the loading of an additional cocatalyst. The doping of Ni greatly improves the visible light absorption and the water splitting activity. With the optimum elemental mole ratio, In/Ga/Zn/Ni = 1/1/1/0.05, H2 and O2 evolution rates achieve 2.23 and 1.15 μmol h−1, respectively.
Co-reporter:Xiao Dong, Li Tian, Jiang Li, Yicheng Zhao, Ye Tian, Yongdan Li
Journal of Power Sources 2014 Volume 249() pp:270-276
Publication Date(Web):1 March 2014
DOI:10.1016/j.jpowsour.2013.10.045
•Single layer fuel cells are fabricated with the mixture of SFM and SDC–Na2CO3.•The fuel cell with 30 wt.% SFM gave the highest 1.05 V OCV and 360 mW cm−2 output.•The single layer cell showed a comparable performance to the three-layer cell.•The effects of the ratio between electronic and ionic conductions are elaborated.A new kind of single layer fuel cell (SLFC) based on a composite material of Ce0.8Sm0.2O2−δ (SDC)–Na2CO3 and Sr2Fe1.5Mo0.5O6−δ (SFM) is successfully fabricated and characterized. As a mixed ionic and electronic conductor, SFM provides more reaction areas than the triple phase boundary provided by a simple mixture of ionic conductor and electronic conductor. SDC–Na2CO3 is used to adjust the ratio of ionic and electronic conductivities. The influence of the SFM content on the electrochemical performance of the SLFC is examined. The pellet made of 30 wt.% SFM and 70 wt.% SDC–Na2CO3 exhibits the highest open circuit voltage of 1.05 V and output of 360 mW cm−2 at 750 °C. Besides, by discussing influence factors of the OCV of the cell, the reason why the SLFC can give a similar OCV and output comparing with the conventional three-layer fuel cell, has been explained in detail.
Co-reporter:Zhengmin Yu, Jianling Meng, Jingran Xiao, Yang Li, Yongdan Li
International Journal of Hydrogen Energy 2014 Volume 39(Issue 28) pp:15387-15393
Publication Date(Web):23 September 2014
DOI:10.1016/j.ijhydene.2014.07.165
•CoSx/TiO2 heterojunction photocatalysts are synthesized.•The CoSx/TiO2 shows remarkable UV and visible light photocatalytic activity.•The hydrogen evolution rate was greatly improved.•The intimate contact of the phases promotes the charge transfer and separation.Cobalt sulfide quantum dots (CoSx QDs) modified TiO2 nanoparticles are prepared with a precipitation-deposition method using TiO2, cobalt acetate and sodium sulfide as the precursors. CoSx QD acts as an effective cocatalyst, which accelerates the transfer of the photo-generated electrons and serves as the active site for the reaction between electrons and H2O, thus enhancing the separation of the e−/h+ pairs and the photocatalytic H2 production activity of TiO2. The amount of CoSx exhibits an optimum value at about 5% (mole ratio to TiO2), at which the H2 production rate achieves 838 μmol h−1 g−1 using ethanol as the sacrificial reagent. This exceeds that of the pure TiO2 by more than 35 times.
Co-reporter:Yang Li, Shaohong Jiang, Jingran Xiao, Yongdan Li
International Journal of Hydrogen Energy 2014 Volume 39(Issue 2) pp:731-735
Publication Date(Web):13 January 2014
DOI:10.1016/j.ijhydene.2013.10.092
•A series of partially nitrided solid solutions have been synthesized.•Energy band engineering was used to tune the band configurations.•The nitrogen oxide split water under visible light with high activity.•The catalysts are stable under visible light during 10 h of reaction.A sort of mixed nitrogen oxides, with a general formula In–Ni–Ta–O–N, has been synthesized with a solid state reaction method and used as the catalyst for visible light (λ > 400 nm) driven overall water splitting without the extra loading of a cocatalyst. Hydrogen and oxygen are evolved with a high rate in an ideal ratio of 2 to 1. The non-nitrided mixed oxide and individual oxide or nitride do not show any activity under the same reaction conditions. The elemental ratio plays a key role and the composition with the best activity is found as In:Ni:Ta:O:N = 0.9:0.1:1:3.21:0.774, with which the sample has an absorption edge at 550 nm.
Co-reporter:Rui Ma;Wenyue Hao;Xiaolei Ma;Ye Tian ; Yongdan Li
Angewandte Chemie 2014 Volume 126( Issue 28) pp:7438-7443
Publication Date(Web):
DOI:10.1002/ange.201402752
Abstract
We report the complete ethanolysis of Kraft lignin over an α-MoC1−x/AC catalyst in pure ethanol at 280 °C to give high-value chemicals of low molecular weight with a maximum overall yield of the 25 most abundant liquid products (LP25) of 1.64 g per gram of lignin. The LP25 products consisted of C6–C10 esters, alcohols, arenes, phenols, and benzyl alcohols with an overall heating value of 36.5 MJ kg−1. C6 alcohols and C8 esters predominated and accounted for 82 wt % of the LP25 products. No oligomers or char were formed in the process. With our catalyst, ethanol is the only effective solvent for the reaction. Supercritical ethanol on its own degrades Kraft lignin into a mixture of small molecules and molecular fragments of intermediate size with molecular weights in the range 700–1400, differing in steps of 58 units, which is the weight of the branched-chain linkage C3H6O in lignin. Hydrogen was found to have a negative effect on the formation of the low-molecular-weight products.
Co-reporter:Rui Ma;Wenyue Hao;Xiaolei Ma;Ye Tian ; Yongdan Li
Angewandte Chemie International Edition 2014 Volume 53( Issue 28) pp:7310-7315
Publication Date(Web):
DOI:10.1002/anie.201402752
Abstract
We report the complete ethanolysis of Kraft lignin over an α-MoC1−x/AC catalyst in pure ethanol at 280 °C to give high-value chemicals of low molecular weight with a maximum overall yield of the 25 most abundant liquid products (LP25) of 1.64 g per gram of lignin. The LP25 products consisted of C6–C10 esters, alcohols, arenes, phenols, and benzyl alcohols with an overall heating value of 36.5 MJ kg−1. C6 alcohols and C8 esters predominated and accounted for 82 wt % of the LP25 products. No oligomers or char were formed in the process. With our catalyst, ethanol is the only effective solvent for the reaction. Supercritical ethanol on its own degrades Kraft lignin into a mixture of small molecules and molecular fragments of intermediate size with molecular weights in the range 700–1400, differing in steps of 58 units, which is the weight of the branched-chain linkage C3H6O in lignin. Hydrogen was found to have a negative effect on the formation of the low-molecular-weight products.
Co-reporter:Jinshuai Yu, Baolong Yu, Yongdan Li
International Journal of Hydrogen Energy 2013 Volume 38(Issue 36) pp:16615-16622
Publication Date(Web):13 December 2013
DOI:10.1016/j.ijhydene.2013.02.113
•Electrochemical performance of catalytic carbon fiber in a direct carbon fuel cell.•Existence of CO2 in cathode gas enhances the fuel cell output.•Direct carbon fuel cell anode oxidation suppresses CO formation.•An anode reaction scheme is proposed based on the results.The electrochemical oxidation of catalytic grown carbon fiber has been examined in a direct carbon fuel cell (DCFC). The single cell contains a composite electrolyte layer made of a samarium doped ceria (SDC) and a eutectic carbonate phase. The cathode is a mixture of lithiated NiO and the composite electrolyte, while the anode is composed of NiO and SDC powder. Catalytic carbon fiber and the eutectic carbonate is premixed and used as the feed of the anode fuel. The effects of the cell pellet configuration, cathode gas composition and the operation temperature on the DCFC performance have been examined in this work. At 700 °C, the maximum power output achieves 112 mW cm−2 with a current density of 249 mA cm−2. The anode off-gas is analyzed with a gas chromatograph, and the Boudouard reaction is found suppressed by the electrical field in the fuel cell operation.
Co-reporter:Zhengmin Yu, Jianling Meng, Yang Li, Yongdan Li
International Journal of Hydrogen Energy 2013 Volume 38(Issue 36) pp:16649-16655
Publication Date(Web):13 December 2013
DOI:10.1016/j.ijhydene.2013.07.056
•A CuO/CF/TiO2 catalyst shows good photocatalytic activity for H2 evolution from ethanol solution.•Co-modification of TiO2 with CuO and carbon fiber enhances the activity greatly.•CuO behaves as the H2 evolution cocatalyst and the carbon fiber serves as the electron transporter.•The activity of CuO/CF/TiO2 is 45 and 2 times higher than those of TiO2 and CuO/TiO2, respectively.•Carbon fiber decreases the solid state interface resistance and charge transfer resistance.An efficient composite catalyst, CuO/CF/TiO2 (where CF represents catalytic grown carbon fiber and TiO2 is the commercial product P25), is prepared with a wet impregnation and calcination process and is applied in the photo stimulated catalytic water splitting. The modification of TiO2 with CuO, serving as the H2 evolution cocatalyst, and carbon fiber, behaving as the electron transporter, enhances greatly the overall activity of the material. The activity of CuO/CF/TiO2 with 1 wt% CF is 45 times higher than that of TiO2 and 2 times higher than that of CuO/TiO2. CF and CuO play a synergistic role in decreasing the recombination rate of the photogenerated carriers in TiO2 bulk phase. The CF in the composite catalyst extends the reaction range, and makes the reaction proceeds on both the surface of CuO intimately contacting with TiO2 particles and the surfaces of the CuO particles which do not in contact with TiO2 but in contact with CF.
Co-reporter:Guangming Zeng, Ruixue Gu, Yongdan Li
International Journal of Hydrogen Energy 2013 Volume 38(Issue 26) pp:11256-11267
Publication Date(Web):30 August 2013
DOI:10.1016/j.ijhydene.2013.06.058
•A shell–core catalyst is formed employing structural memory effect of a mixed oxide.•The shell–core Ni/Mg–Al catalyst shows perfect activity in ethanol steam reforming.•The shell–core catalyst performs much better than the bulk one.•The reaction temperature and space-time affect the product distribution.•C2H4 is observed at very low space-time.The structural “memory effect” of a hydrotalcite (HT)-derived mixed oxide is utilized to prepare a shell–core Ni/Mg–Al catalyst for ethanol steam reforming (ESR). The reconstruction proceeds rapidly in a Ni2+ nitrate solution on the outer layer of the Mg–Al mixed oxide particle, being accompanied with the growth of large flake-like sheets. A part of Ni2+ ions can incorporate into the reconstructed HT-like structure, leading to the formation of the shell-type Ni loading catalyst after calcination. At 700 °C, the shell–core catalysts with much lower Ni contents perform better activities than that of the bulk Ni/Mg–Al catalyst prepared directly via the calcination of the HT-like precursor. Further investigations reveal that temperature and space-time significantly affect the contribution of WGS, CH4 reforming reactions to the product distribution in the ESR reaction. Most interestingly, C2H4 is observed in the reactions carried out at 700 °C and very low space-time.
Co-reporter:Yicheng Zhao, Zhuoran Xu, Chun Xia, Yongdan Li
International Journal of Hydrogen Energy 2013 Volume 38(Issue 3) pp:1553-1559
Publication Date(Web):6 February 2013
DOI:10.1016/j.ijhydene.2012.11.004
The direct current four-probe method has been employed to investigate the conduction of oxide ion and proton in a doped ceria–carbonate composite electrolyte for fuel cells. The measurements are conducted in oxygen and in hydrogen atmospheres in the temperature range of 425–650 °C. The conductivities of both of O2− and H+ increase with the increase of carbonate content above the melting point of the carbonate. The ionic conductivities of the composite electrolytes have also been simulated using the effective medium percolation theory. The deviations between experimental results and simulated values of O2− conductivity are caused by the associating effect of ceramic and carbonate phases, which leads to a higher O2− migration energy through the phase interface. According to the comparison of experimental data and simulated values, the conduction mechanisms of O2− and H+ have been proposed.Highlights► The conductivities of H+ and O2− are measured by the four-probe method. ► The effective medium percolation theory is used to simulate the ionic conductivity. ► The effects of sample composition and temperature on its conductivity are reported. ► The O2− conduction through the phase interface needs a higher activation energy. ► The conduction mechanisms of H+ and O2− are investigated.
Co-reporter:Yicheng Zhao, Chun Xia, Lijun Jia, Zhiming Wang, Hongjiao Li, Jinshuai Yu, Yongdan Li
International Journal of Hydrogen Energy 2013 Volume 38(Issue 36) pp:16498-16517
Publication Date(Web):13 December 2013
DOI:10.1016/j.ijhydene.2013.07.077
•The development of composite electrolyte and ionic conduction in it are reviewed.•Four kinds of electrolyte for direct carbon fuel cell are summarized.•The carbon electrochemical oxidation in direct carbon fuel cell is discussed.•Anode materials for direct hydrocarbon solid oxide fuel cell are reviewed.A solid oxide fuel cell (SOFC) is a promising energy conversion device with high efficiency and low pollutant emission. The practical application of the conventional SOFCs is limited mainly because of their high operating temperature and the inconvenience brought by the H2 fuel utilization. This work reviews the recent progress on intermediate temperature SOFCs especially with non-hydrogen fuels. Composite electrolyte consisting of a solid oxide ionic conducting phase and a molten carbonate phase exhibits sufficient ionic conductivity in the intermediate temperature range, i.e. 500–800 °C, and facilitates the simultaneous conduction of H+, O2− and CO32− ions. A single cell with the composite electrolyte shows a promising power density, 1700 mW cm−2 at 650 °C with hydrogen as the fuel. The composite electrolyte has been also employed in a direct carbon fuel cell (DCFC), and the simultaneous conduction of O2− and CO32− in the electrolyte has been proposed. Recently, perovskite structured materials are found to have good resistance to coke formation as the anode of the direct hydrocarbon solid oxide fuel cell, and several carbon resistant perovskite anodes are employed in all-perovskite structured SOFCs, which exhibit excellent performance with CH4 and methanol as the fuel.
Co-reporter:Yang Li, Zhengmin Yu, Jianling Meng, Yongdan Li
International Journal of Hydrogen Energy 2013 Volume 38(Issue 10) pp:3898-3904
Publication Date(Web):1 April 2013
DOI:10.1016/j.ijhydene.2013.01.077
In this work, effort has been made to design an efficient catalyst for the photo-stimulated water splitting reaction, starting with the modification of TiO2 (P25) to enhance its activity. A SiC(1 wt%)–TiO2 composite material shows an activity as high as twice of that of TiO2. NiOx, an electron collector, promotes the activity of TiO2, while IrO2, a hole capturer, enhances the hydrogen evolution rate of SiC. A SiC(1 wt%)–NiOx/TiO2 three-component and an IrO2/SiC(1 wt%)–NiOx/TiO2 four-component composite materials produce 30% and 100% more H2 than the NiOx/TiO2 catalyst during the first 5 h, respectively, with ethanol used as the sacrificial reagent. Furthermore, the SiC(1 wt%)–NiOx/TiO2 catalyst is active under visible light, while the NiOx/TiO2 catalyst shows no activity under the same irradiation condition. 3C-SiC has a narrow band gap and its band edge well compensates that of the TiO2. The enhancing effect of dopants on the SiC(1 wt%)–TiO2 composite material is sensitive to the location of the modifiers, which further proves that an efficient separation of the charge carriers is crucial to the overall activity of the composite catalyst.Graphical abstractHighlights► A non-metallic semiconductor is used as a promoter of TiO2 for water splitting. ► The SiC modified catalysts exhibit excellent activities in hydrogen evolution. ► The composite catalysts are active under visible light and enough stable. ► Directional movement of the charge carriers in the composites is proposed.
Co-reporter:He Li, Hong Chen, Mingfa Yao, and Yongdan Li
Industrial & Engineering Chemistry Research 2013 Volume 52(Issue 2) pp:686
Publication Date(Web):December 26, 2012
DOI:10.1021/ie303340n
The intrinsic kinetics of the catalytic combustion of a trace amount of ethylene in a CO2 stream over a Cu–Mn–O catalyst prepared with a coprecipitation method is investigated. The experiments are carried out in a fixed-bed reactor with 0.3 g of catalyst in a low temperature range (470 to 620 K) and varying the concentration of C2H4 and O2 in the feed stream. The power rate law, Langmuir–Hinshelwood (LH), Eley–Rideal (ER), and Mars–van Krevelen (MVK) models are compared. The residual error distribution of the ethylene conversion is employed to optimize the model equations. The extended MVK model containing desorption terms of the combustion products fit the data well. The pilot test with a fixed-bed reactor and a commercial feed stream is carried out, and the macro kinetic equations are obtained. Combined with the extended MVK model equations of the intrinsic kinetics, the effectiveness factor is calculated, which gives further prediction of the performance of the extruded catalyst under commercial conditions.
Co-reporter:Gaowei Wang, Yi Jin, Guojuan Liu, and Yongdan Li
Energy & Fuels 2013 Volume 27(Issue 8) pp:4448-4456
Publication Date(Web):January 23, 2013
DOI:10.1021/ef3019707
A Ni–Fe–Al catalyst derived from a hydrotalcite-like structured precursor prepared with a co-precipitation technique is employed in the methane catalytic decomposition reaction producing carbon nanofibers (CNFs) and COx-free hydrogen. The effect of doping with iron on the activity and stability is investigated. The performance of the catalyst is evaluated with a temperature-programmed reaction and a constant temperature reaction. The catalyst with a Ni/Fe/Al mole ratio of 2:1:1 shows an extremely stable activity and is still active after 210 h of reaction. The carbon yield on this catalyst reaches 562 g of C/g of catalyst. The post-reaction characterization results indicate that the Ni–Fe alloy is formed in the Ni–Fe–Al catalyst and is proposed to be the active phase for the CNF growth. The addition of an appropriate amount of Fe may enhance the carbon diffusion rate and decrease the carbon formation rate. Thus, the balance among the carbon atom formation, diffusion, and precipitation rates is maintained, and the stability of the catalyst is enhanced.
Co-reporter:Ruixue Gu;Guangming Zeng;Jingjing Shao
Frontiers of Chemical Science and Engineering 2013 Volume 7( Issue 3) pp:270-278
Publication Date(Web):2013 September
DOI:10.1007/s11705-013-1337-2
A macro-meso-porous monolithic Ni-based catalyst was prepared via an impregnation route using polystyrene foam as the template and then used in the steam reforming of ethanol to produce a H2-rich gas. The Ni/Mg-Al catalyst has a hierarchically macro-meso-porous structure as indicated by photographs and scanning electron microscopy (SEM). The surface area of the catalyst was 230 m2·g−1 and the Ni dispersion was 5.62%. Compared to the pelletized sample that was prepared without a template, the macro-meso-porous Ni/Mg-Al monolith exhibited superior reactivity in terms of H2 production and also had lower CH4 yields at 700°C and 800°. Furthermore, the monolithic catalyst maintained excellent activity and H2 selectivity after 100-h on-stream at 700°, as well as good resistance to coking and metal sintering.
Co-reporter:Le Yang, Wei Zhou, K. Seshan, Yongdan Li
Journal of Molecular Catalysis A: Chemical 2013 Volumes 368–369() pp:61-65
Publication Date(Web):March 2013
DOI:10.1016/j.molcata.2012.11.024
The conversion of guaiacol to catechol in high temperature water by catalysis of mineral hydrochloric acid is examined. The effects of pH and H2 pressure are measured in the conversion of guaiacol. Hydrogen enhances the reaction dramatically. Moreover, low pH and high hydrogen pressure favor the reaction. The highest conversion of guaiacol and best yield of catechol of 99% and 89%, respectively, are achieved with 1 MPa hydrogen at pH = 1.8 for 3 h at 280 °C. Based on the experimental results and kinetics, possible reaction mechanisms are proposed. Besides ionic mechanism and water catalysis, hydrogen polarization also occurred without metal catalyst.Graphical abstractHighlights► High yield of catechol from guaiacol is obtained. ► Hydrogen chloride is the best catalyst. ► pH decides the kinetics and the reaction mechanism. ► High hydrogen partial pressure enhances the reaction.
Co-reporter:Dapeng Zhang, Qinghua Liu, Xiaosong Shi, Yongdan Li
Journal of Power Sources 2012 Volume 203() pp:201-205
Publication Date(Web):1 April 2012
DOI:10.1016/j.jpowsour.2011.10.136
Tetrabutylammonium hexafluorophosphate (TEAPF6) and 1-ethyl-3-methyl imidazolium hexafluorophosphate (EMIPF6) are synthesized and used as the supporting electrolytes of a non-aqueous redox flow battery using vanadium acetylacetonate (V(acac)3) as the active species. The conductivity and cyclic voltammograms of the electrolytes of the two ionic liquids are measured. The cyclic voltammograms show that both of them are stable in an operating potential range (−2.5–1.5 V). The diffusion coefficients of V(acac)3 in the electrolytes are determined as 0.92–1.47 × 10−6 cm2 s−1 in 0.5 mol l−1 TEAPF6 and 2.35–3.79 × 10−6 cm2 s−1 in 0.5 mol EMIPF6, respectively. The charge–discharge performances of the two non-aqueous V(acac)3 containing electrolytes with TEAPF6 and EMIPF6 as the supporting electrolytes are evaluated in an H-type glass cell. The coulombic efficiencies are measured as in the range of 53.31–57.44% at 50% state of charge with an electrolyte containing 0.2 mol l−1 TEAPF6, and as in the range of 46.04–43.46% for the electrolyte containing EMIPF6 with the same concentrations of the components.Graphical abstractHighlights► Two ionic liquids are used in the V(acac)3 redox flow battery. ► Cyclic voltammograms and kinetics of reactions are tested. ► Charge–discharge performance shows a reasonable coulombic efficiency.
Co-reporter:Dapeng Zhang, Huajie Lan, Yongdan Li
Journal of Power Sources 2012 Volume 217() pp:199-203
Publication Date(Web):1 November 2012
DOI:10.1016/j.jpowsour.2012.06.038
A single-metal redox flow battery employing bis(acetylacetone)ethylenediamine cobalt(II) as the active species and tetrabutylammonium hexafluorophosphate as the supporting electrolyte with acetonitrile as the solvent has been examined. Cyclic voltammetry is used to measure the electrode kinetics of the anodic and cathodic reactions. Three redox couples are observed in the stable potential window, these electrode reactions are quasi-reversible and together yield a cell potential of 2.0 V. The disproportion reactions of active species are controlled by the diffusion coefficient. The effect of the environmental factors, such as temperature, oxygen and water, has been tested in the experiment. The charge–discharge characteristics of this system are evaluated in an H-type glass cell. The coulombic efficiencies 90.24% and 87.88% in cycle 5 and cycle 8 are obtained, respectively, with 1 mA charge 0.5 mA discharge current.Graphical abstractHighlights► Co(acacen) was synthesized and evaluated in a non-aqueous redox flow battery. ► Cell potential for one-electron disproportionation was 2.0 V. ► Charge–discharge performance shows a good coulombic efficiency. ► The effect of the environmental factors has been evaluated.
Co-reporter:Yicheng Zhao, Chun Xia, Yujie Wang, Zhuoran Xu, Yongdan Li
International Journal of Hydrogen Energy 2012 Volume 37(Issue 10) pp:8556-8561
Publication Date(Web):May 2012
DOI:10.1016/j.ijhydene.2012.02.053
A composite electrolyte consisting of a samarium doped ceria and a binary eutectic carbonate phase is investigated in this work. It has been found that O2−/H+ conductions take place when H2 and O2 used as the reactants. The presence of CO2 in the cathode gas leads to the appearance of CO32− conduction. The overall conductivity of the composite electrolyte is measured with a current-interruption technique and the ions transferred by O2−/H+/CO32− respectively are obtained by a quantitative measurement of the reaction products, i.e. H2O and CO2. The change of the carbonate content in the composite electrolyte presents a great influence on the conductivity of each ion. According to these experimental facts, the pathways for the individual ionic conductions are proposed.Highlights► The current-interrupt method is used to measure the total ionic conductivity. ► The products of the single cell operation are quantitatively analyzed. ► H+, O2− and CO32− conductions in the ceria-carbonate electrolyte are proved. ► The comparative importance of the three ionic conductions is determined. ► The conduction mechanisms of H+, O2− and CO32− are proposed.
Co-reporter:Hongjiao Li, Ye Tian, Zhiming Wang, Fuchang Qie and Yongdan Li
RSC Advances 2012 vol. 2(Issue 9) pp:3857-3863
Publication Date(Web):12 Mar 2012
DOI:10.1039/C2RA01256A
A chemically stable perovskite material Sr2Fe1.5Mo0.5O6 (SFMO) is employed as the anode of a solid oxide fuel cell (SOFC). An electrolyte-supported single cell with anode, electrolyte and cathode all made of perovskite structured materials and with a configuration of SFMO|La0.8Sr0.2Ga0.83Mg0.17O3|Ba0.5Sr0.5Co0.8Fe0.2O3 (SFM|LSGM|BSCF) is fabricated by a screen printing method. The single cell gives a maximum power density of 391 mW cm−2 for CH3OH, and 520 mW cm−2 for H2 as the fuel, respectively, at 1073 K with oxygen as the oxidant gas. The mass spectra of the flue gas out of the test reactor confirm that methanol thermally decomposes inside the anode chamber and generates mainly CO and H2 at 1023 K. Analysis of the after-test cell tells that the anode surface has no carbon formation under reaction with methanol as the feed for 3 h. The carbon resistance is attributed to the fact that the anode is in oxide state which cannot facilitate the formation of bulk carbon with graphite structure. The fast activation and gasification of the carbon species by the oxidative atmosphere around the anode surface are also beneficial factors. The test results indicate also that the activation of CH3OH is much more difficult than that of H2.
Co-reporter:Yicheng Zhao, Chun Xia, Zhuoran Xu, Yongdan Li
International Journal of Hydrogen Energy 2012 Volume 37(Issue 15) pp:11378-11382
Publication Date(Web):August 2012
DOI:10.1016/j.ijhydene.2012.05.015
A hydrogen and oxygen electrochemical pump technique has been employed to elucidate the conduction of proton and oxygen ion in a doped ceria–carbonate composite electrolyte for intermediate temperature solid oxide fuel cells. The composite material shows efficient conductivities of both of the two ions at 650 °C. The molten carbonate phase is important for the migration of both of the two ions. The mechanism of the conduction of proton and oxygen ion is also discussed.Graphical abstractHighlights► The gas electrochemical pumps are used to study the conductions of H+ and O2−. ► H+ and O2− conductions in the ceria–carbonate electrolyte are proved. ► The effects of the carbonate content and the operating temperature are examined. ► The conduction mechanisms of H+ and O2−are proposed.
Co-reporter:Jihui Wang, Hong Chen, Ye Tian, Mingfa Yao, Yongdan Li
Fuel 2012 Volume 97() pp:805-811
Publication Date(Web):July 2012
DOI:10.1016/j.fuel.2012.03.008
A thermodynamic analysis of hydrogen production from oxidative steam reforming (OSR) of methanol has been carried out by a Gibbs free energy minimization method. The equilibrium yields of hydrogen, carbon monoxide, methane and coke as a function of H2O/MeOH ratio (0.0–10.0), O2/MeOH ratio (0.0–1.0), and temperature (200 °C, 400 °C, 600 °C, 800 °C) at 0.1 MPa are investigated. Methanol can be fully converted at any H2O/MeOH and O2/MeOH ratio in the condition range evaluated. Methane is the main product at low temperatures (200 °C, 400 °C), while hydrogen and carbon monoxide become dominant products with the increase of the temperature. 600 °C is favorable for hydrogen production at which the highest hydrogen yield appears. Carbon monoxide yield increases monotonically with the increase of the temperature and shows its maximum at 800 °C. An increase of the H2O/MeOH ratio leads to a preference for hydrogen production as well as an inhibition of the formation of carbon monoxide, methane and coke. The major contribution of adding oxygen is lowering the energy supply and suppressing the potential of coke formation at low H2O/MeOH ratio. However, the total oxidation of methanol tends to dominant in this case. For the purpose of producing hydrogen-rich gas, no oxygen addition is preferred. The favorable operation window is obtained as 600 °C, H2O/MeOH ratio = 6.0–8.0 and O2/MeOH ratio = 0. Under this optimal condition, 2.77–2.84 mol/mol methanol hydrogen yield and 0.13–0.17 mol/mol methanol carbon monoxide yield with trace amount methane (0.0070–0.017 mol/mol methanol) can be achieved without the risk of carbon deposition.Graphical abstractHighlights► A thermodynamics analysis of the oxidative steam reforming of methanol. ► Water favors hydrogen production and the suppression of by-products. ► Oxygen addition lowers hydrogen yield significantly. ► Optimal conditions are 600 °C, H2O/MeOH ratio = 6.0–8.0 and O2/MeOH ratio = 0. ► The potential of methane formation at low temperatures is very high.
Co-reporter:Zebao Rui, Jingjing Ding, Lining Fang, Y.S. Lin, Yongdan Li
Fuel 2012 Volume 94() pp:191-196
Publication Date(Web):April 2012
DOI:10.1016/j.fuel.2011.10.073
Oxyfuel combustion, using O2/CO2 mixed gas as the oxidant, increases CO2 concentration in the flue gas and reduces the cost of CO2 capture. Nevertheless, the cost of oxygen production is a key to make the process a viable future option. In this work, YBaCo4O7+δ (YBC114) sorbent with a layered hexagonal structure was prepared and used to produce the O2–CO2 gas mixture at a low temperature (200–400 °C). YBC114 has both the ability of temperature swinging oxygen absorption/desorption (TSA) and the property of pressure swinging oxygen absorption/desorption (PSA) in the temperature range of 200–400 °C. The XRD patterns show that YBC114 has a good stability in both the O2-containing and CO2-containing atmosphere at 200–400 °C. Cyclic operation for the low temperature O2-enriched CO2 stream production indicates that YBC114 has high cyclic stability. The absorption/desorption kinetics can be improved by combining PSA with TSA at no cost of the O2 absorption capacity. For such a design, oxygen is absorbed when YBC114 is heated from 200 °C to 345 °C with a slow ramping rate in an air stream. Oxygen is desorbed and an oxygen-enriched carbon dioxide stream is obtained when YBC114 is exposed in a carbon dioxide stream and cooled from 345 °C to 200 °C. It has been found that the synthesis method of the YBC114 also has a significant effect on the oxygen absorption/desorption kinetics.Highlights► YBaCo4O7+δ (YBC114) is used to produce the O2–CO2 gas mixture at 200–400 °C. ► YBC114 shows good stability in the O2-containing or CO2-containing atmosphere. ► Effect of synthesis method is studied. ► Pressure and temperature swinging oxygen absorption/desorption are coupled.
Co-reporter:Zhiming Wang, Ye Tian, Yongdan Li
Journal of Power Sources 2011 Volume 196(Issue 15) pp:6104-6109
Publication Date(Web):1 August 2011
DOI:10.1016/j.jpowsour.2011.03.053
A double-perovskite Sr2FeMoO6 (SFMO) has been synthesized with a combined citrate-EDTA complexing method. The material shows a double-perovskite structure after reduction in 5% H2/Ar at 1100 °C for 20 h. A single fuel cell using this material as anode is constructed with the configuration of SFMOǀLa0.8Sr0.2Ga0.83Mg0.17O3ǀBa0.5Sr0.5Co0.8Fe0.2O3. The cell exhibits a remarkable electrochemical activity in both H2 and dry CH4, respectively. With Oxygen as oxidant, the maximum power density is 863.7 mW cm−2 with H2 as the fuel and 604.8 mW cm−2 with dry CH4 as the fuel at 850 °C, respectively. SFMO has an almost linear thermal expansion coefficient from 30 to 900 °C and is very close to that of La0.8Sr0.2Ga0.83Mg0.17O3. A durability test of the single cell indicates that SFMO is stable in dry CH4 operation. Therefore SFMO can be recommended as a promising anode material for LaGaO3-based solid oxide fuel cells operating with both H2 and dry CH4.Graphical abstractHighlights► Double-perovskite Sr2FeMoO6 can be used as anode material for solid oxide fuel cell. ► No buffer layer between the anode and electrolyte is needed in the cell. ► The maximum power density is 863.7 mW cm−2 with H2 at 850 °C. ► The maximum power density is 604.8 mW cm−2 with dry CH4 at 850 °C. ► Sr2FeMoO6 anode gives a stable performance in H2 and dry CH4.
Co-reporter:Lijun Jia, Ye Tian, Qinghua Liu, Chun Xia, Jinshuai Yu, Zhiming Wang, Yicheng Zhao, Yongdan Li
Journal of Power Sources 2010 Volume 195(Issue 17) pp:5581-5586
Publication Date(Web):1 September 2010
DOI:10.1016/j.jpowsour.2010.03.016
A composite electrolyte containing a Li/Na carbonate eutectic and a doped ceria phase is employed in a direct carbon fuel cell (DCFC). A four-layer pellet cell, viz. cathode current collector (silver powder), cathode (lithiated NiO/electrolyte), electrolyte and anode current collector layers (silver powder), is fabricated by a co-pressing and sintering technique. Activated carbon powder is mixed with the composite electrolyte and is retained in the anode cavity above the anode current collector. The performance of the single cell with variation of cathode gas and temperature is examined. With a suitable CO2/O2 ratio of the cathode gas, an operating temperature of 700 °C, a power output of 100 mW cm−2 at a current density of 200 mA cm−2 is obtained. A mechanism of O2− and CO32− binary ionic conduction and the anode electrochemical process is discussed.
Co-reporter:Chun Xia, Yi Li, Ye Tian, Qinghua Liu, Zhiming Wang, Lijun Jia, Yicheng Zhao, Yongdan Li
Journal of Power Sources 2010 Volume 195(Issue 10) pp:3149-3154
Publication Date(Web):15 May 2010
DOI:10.1016/j.jpowsour.2009.11.104
The performance of a composite electrolyte composed of a samarium doped ceria (SDC) and a binary eutectic carbonate melt phase has been examined. This material shows higher ionic conductivity than pure SDC in intermediate temperature region. SDC with different morphologies is obtained by co-precipitation, sol–gel and glycine-nitrate combustion preparation techniques. A tri-layer single cell is prepared with a cost-effective co-pressing and co-sintering technique. It is found that the surface properties of SDC and the electrolyte thickness have a great influence on the fuel cell performance. When the co-precipitated SDC is used as the electrolyte component and CO2/O2 gas mixture is adopted as the cathode oxidant gas, a fuel cell with an excellent performance is obtained, which has a peak power output of 1704 mW cm−2 at a current density of 3000 mA cm−2 at 650 °C. The influence of cathode atmosphere is examined with conductivity measurement and fuel cell performance test. The results support the concept of O2−/H+/CO32− ternary conduction.
Co-reporter:Qinghua Liu, Ye Tian, Hongjiao Li, Lijun Jia, Chun Xia, Levi T. Thompson, Yongdan Li
Journal of Power Sources 2010 Volume 195(Issue 19) pp:6532-6538
Publication Date(Web):1 October 2010
DOI:10.1016/j.jpowsour.2010.04.048
A methane catalytic decomposition reactor-direct carbon fuel cell-internal reforming solid oxide fuel cell (MCDR-DCFC-IRSOFC) energy system is highly efficient for converting the chemical energy of methane into electrical energy. A gas turbine cycle is also used to output more power from the thermal energy generated in the IRSOFC. In part I of this work, models of the fuel cells and the system are proposed and validated. In this part, exergy conservation analysis is carried out based on the developed electrochemical and thermodynamic models. The ratio of the exergy destruction of each unit is examined. The results show that the electrical exergy efficiency of 68.24% is achieved with the system. The possibility of further recovery of the waste heat is discussed and the combined power-heat exergy efficiency is over 80%.
Co-reporter:Qinghua Liu, Ye Tian, Hongjiao Li, Lijun Jia, Chun Xia, Levi T. Thompson, Yongdan Li
Journal of Power Sources 2010 Volume 195(Issue 19) pp:6539-6548
Publication Date(Web):1 October 2010
DOI:10.1016/j.jpowsour.2010.04.047
A highly efficient integrated energy conversion system is built based on a methane catalytic decomposition reactor (MCDR) together with a direct carbon fuel cell (DCFC) and an internal reforming solid oxide fuel cell (IRSOFC). In the MCDR, methane is decomposed to pure carbon and hydrogen. Carbon is used as the fuel of DCFC to generate power and produce pure carbon dioxide. The hydrogen and unconverted methane are used as the fuel in the IRSOFC. A gas turbine cycle is also used to produce more power output from the thermal energy generated in the IRSOFC. The output performance and efficiency of both the DCFC and IRSOFC are investigated and compared by development of exact models of them. It is found that this system has a unique loading flexibility due to the good high-loading property of DCFC and the good low loading property of IRSOFC. The effects of temperature, pressure, current densities, and methane conversion on the performance of the fuel cells and the system are discussed. The CO2 emission reduction is effective, up to 80%, can be reduced with the proposed system.
Co-reporter:Hongjiao Li, Qinghua Liu, Yongdan Li
Electrochimica Acta 2010 Volume 55(Issue 6) pp:1958-1965
Publication Date(Web):15 February 2010
DOI:10.1016/j.electacta.2009.11.015
The electrochemical oxidation of carbon at the anode of a direct carbon fuel cell (DCFC) includes charge transfer steps and chemical steps. A microstructural model of carbon particle is built, in which perfect graphene stacks are taken as the basic building blocks of carbon. A modified mechanism taking account of the irreversibility of the process and supposing that the electrochemical oxidation of carbon takes place only at the edges of the graphene sheets is proposed. A Tafel type overall rate equation is deduced along with expressions of exchange current density (j0) and activation polarization (ηact). The performance of carbon black and graphite as the fuel of DCFC is examined. It has been found that j0 is in the range of 0.10–6.12 mA cm−2 at 923–1123 K and ηact is in the range of 0.024–0.28 V at 923–1123 K with current density in 10–120 mA cm−2. Analysis of the j0, ηact values and the product composition reveals that the charge transfer steps as well as the oxygen ion absorption steps are both important for the reaction rate. The activity of the carbon material with respect to atom location is introduced to the open circuit potential difference (OCP) calculation with Nernst equation.
Co-reporter:Yun Jin, Zebao Rui, Ye Tian, Yuesheng Lin, Yongdan Li
International Journal of Hydrogen Energy 2010 Volume 35(Issue 13) pp:6691-6698
Publication Date(Web):July 2010
DOI:10.1016/j.ijhydene.2010.04.042
Hydrogen production via oxidative steam reforming of ethanol in a dense tubular membrane reactor (DMR) is sequentially simulated with ASPEN PLUS. The DMR is divided into multi-sub-reactors, and the Gibbs free energy minimization sub-model in ASPEN PLUS is employed to simulate the oxidative steam reforming of ethanol process in the sub-reactors. A FORTRAN sub-routine is integrated into ASPEN PLUS to simulate the oxygen permeation through membranes in the sub-separators. The simulation result indicates that there is an optimal length of the tubular membrane reactor at the operating temperature and steam-to-ethanol (H2O/EtOH) ratio, under which hydrogen and carbon monoxide formation reach their maxima.
Co-reporter:Guangming Zeng, Ye Tian, Yongdan Li
International Journal of Hydrogen Energy 2010 Volume 35(Issue 13) pp:6726-6737
Publication Date(Web):July 2010
DOI:10.1016/j.ijhydene.2010.03.099
A thermodynamic analysis of hydrogen production from propane by oxidative steam reforming (OSR) is performed with a Gibbs free energy minimization method. Addition of oxygen reduces the enthalpy of the system and facilitates the heat supply. Equilibrium compositions of OSR as a function of temperature (300, 500, 700 and 900 °C), H2O/C3H8 ratio (1.0–20.0) and O2/C3H8 ratio (0.0–2.0) under oxidative and thermo-neutral (TN) conditions are evaluated. The results for oxidative conditions demonstrate that at 700 °C with H2O/C3H8 ratios above 7.0 and/or O2/C3H8 ratios higher than 1.3 are beneficial for hydrogen production which facilitates superior hydrogen yield, i.e. close to 9.0 mol/mol propane, with coke and methane formation reactions being suppressed effectively. For TN condition, autothermal temperature and equilibrium composition have a stronger dependence on O2/C3H8 ratio than on H2O/C3H8 ratio. Further calculations show that the condition at 700 °C with an appropriate H2O/C3H8 ratio between 7.0 and 13.0 is favorable for achieving a high hydrogen yield and a low carbon monoxide yield. Therefore, a favorable operational range is proposed to ensure the most optimized product yield.
Co-reporter:Xinli Tong, Yang Ma, Yongdan Li
Carbohydrate Research 2010 Volume 345(Issue 12) pp:1698-1701
Publication Date(Web):16 August 2010
DOI:10.1016/j.carres.2010.05.019
The renewable furan-based platform chemical, 5-hydroxymethylfurfural (HMF), has been efficiently synthesized from d-fructose and sucrose in the presence of a catalytic amount of protic ionic liquids. The 1-methylimidazolium-based and N-methylmorpholinium-based ionic liquids are employed. As a result, 74.8% and 47.5% yields of HMF are obtained from d-fructose and sucrose, respectively, at 90 °C for 2 h under nitrogen atmosphere when N-methylmorpholinium methyl sulfonate ([NMM]+[CH3SO3]−) is used as the catalyst in an N,N-dimethylformamide–lithium bromide (DMF–LiBr) system. The acidities of ionic liquids are determined by the Hammett method, and the correlation between acidity and catalytic activity is discussed. Moreover, the effects of reaction temperature and time are investigated, and a plausible reaction mechanism for the dehydration of d-fructose is proposed.
Co-reporter:Xinli Tong Dr.
ChemSusChem 2010 Volume 3( Issue 3) pp:350-355
Publication Date(Web):
DOI:10.1002/cssc.200900224
Abstract
The dehydration of D-fructose and glucose has been studied with acidic ionic liquids as catalysts. A series of Brønsted-acidic ionic liquids has been synthesized and tested in the dehydration of D-fructose. The results showed that N-methyl-2-pyrrolidonium methyl sulfonate [NMP]+[CH3SO3]− and N-methyl-2-pyrrolidonium hydrogen sulfate [NMP]+[HSO4]− have high catalytic activity. Highly efficient and selective dehydration of D-fructose to 5-hydroxymethylfurfural (HMF) was achieved in dimethyl sulfoxide (DMSO) under mild conditions. For example, a 72.3 % yield of HMF with 87.2 % selectivity were obtained for 2 h at 90 °C in the presence of 7.5 mol % [NMP]+[CH3SO3]−. The effects of the reaction temperature, time, and solvent were investigated in detail. The catalyst and solvent can be recycled for the dehydration of D-fructose. The Hammett method was used to determine the acidities of these ionic liquids, which indicated that the acidity and molecular structure have strong effects on the catalytic activity of ionic liquids. Based on the experimental results, a possible reaction mechanism for the dehydration of D-fructose is proposed.
Co-reporter:Zebao Rui, Jingjing Ding, Yongdan Li, Y.S. Lin
Fuel 2010 Volume 89(Issue 7) pp:1429-1434
Publication Date(Web):July 2010
DOI:10.1016/j.fuel.2009.10.024
Perovskite-type SrCo0.8Fe0.2O3−δ (SCF) has been prepared by a liquid citrate method and used to produce O2–CO2 gas mixture for oxyfuel combustion. Oxygen is desorbed and an oxygen-enriched carbon dioxide stream is obtained when SCF is exposed in a carbon dioxide stream at high temperature. Oxygen is adsorbed when SCF is regenerated in an air stream. A carbonation-reaction mechanism for O2-desorption has been identified with the evidences of XRD and TGA analysis. It is found that the theoretical oxygen sorption capacity decreases with the increase of temperature. The sorption kinetics over a temperature range of 700–900 °C has been examined by TGA experiment. Both desorption and sorption processes exhibit a high reaction rate in an initial stage followed by a slower rate in a second stage. It is difficult to reach the theoretical oxygen sorption capacity during the whole temperature range due to the slow oxygen desorption rate. Optimal temperatures for oxygen sorption and desorption processes are determined to be 900 and 850 °C, respectively. Multiple sorption and desorption cycles indicate that SCF sorbent has high reactivity and cyclic stability. Comparison with the reference La0.1Sr0.9Co0.5Fe0.5O2.6 (LSCF) and Sr0.5Ca0.5Co0.5Fe0.5O2.47 (SCCF) sorbents shows that SCF has faster carbonation reaction at high temperature, i.e., 850 and 900 °C, and much higher theoretical oxygen sorption capacities.
Co-reporter:Ailing Qiao, Ke Zhang, Ye Tian, Lili Xie, Huajiang Luo, Y.S. Lin, Yongdan Li
Fuel 2010 Volume 89(Issue 6) pp:1274-1279
Publication Date(Web):June 2010
DOI:10.1016/j.fuel.2009.12.006
Pd–Cu alloy membrane was prepared by electroless plating on porous stainless steel (PSS) support. Sol–gel derived ceria was introduced as the intermediate layer by a sol-dip-coating method to prevent intermetallic diffusion and to enhance the affinity between the support and membrane. Ceria layer moderates the pore size and porosity of the support effectively to meet the needs of the alloy layer deposition. Permeation test was carried out in a high temperature range, i.e. 573–773 K with a pressure difference of 0.1 MPa. The results showed that properly prepared ceria layer was effective as the diffusion barrier in the temperature range examined, which is suitable for water–gas shift reaction. The performance of the membranes in this work is also compared with that in our previous work in which pure Pd membrane and yttrium stabilized zirconia intermediate layer were examined.
Co-reporter:Chun Xia, Yi Li, Ye Tian, Qinghua Liu, Yicheng Zhao, Lijun Jia, Yongdan Li
Journal of Power Sources 2009 Volume 188(Issue 1) pp:156-162
Publication Date(Web):1 March 2009
DOI:10.1016/j.jpowsour.2008.11.068
The performance of a composite electrolyte composed of a samarium doped ceria (SDC) and a ternary eutectic carbonate melt phase was examined. The formation temperature of a continuous carbonate melt phase is crucial to the high conductivity of this material. The electrolyte contains 30 and 50 wt% carbonate exhibited a sharp increase of conductivity at a temperature close to the melting point of the eutectic carbonate, ca 400 °C, which is more than 100 °C lower than those electrolytes using binary carbonate. At around 650 °C, and with CO2/O2 used as the cathode gas, the fuel cell gave a power output 720 mW cm−2 at a current density 1300 mA cm−2. Water was measured in both the anode and cathode outlet gases and CO2 was detected in the anode outlet gas. When discharged at 800 mA cm−2, a stable discharge plateau was obtained. The CO2 in the cathode gas enhances the power output and the stability of the single cell. Based on these experimental facts, a ternary ionic conducting scheme is proposed and discussed.
Co-reporter:Douxing Li, Jiuling Chen, Yongdan Li
International Journal of Hydrogen Energy 2009 Volume 34(Issue 1) pp:299-307
Publication Date(Web):January 2009
DOI:10.1016/j.ijhydene.2008.09.106
A coprecipitated Ni–Cu/Al2O3 catalyst was examined in a fluidized bed reactor for the decomposition of methane to COx-free hydrogen and carbon nanofibers using two different reaction temperature schemes, i.e. constant temperature and pre-induction operation. At constant temperatures, the catalyst showed quasi-stable activity below 913 K for a notable time period, while its performance decayed fast above this temperature and a quick deactivation was observed at 1013 K. However, for reaction at 1013 K, the durability was improved if the catalyst was induced for 10 min at 823 K in the reaction atmosphere. A detailed examination of the metal particles after reaction with EDS revealed that the composition of the metal particle depended strongly on the reaction temperature and the induction scheme. The metal particles in the reduced catalyst showed a composition deviation also. The HRTEM micrographs of the carbon–metal interface and the EDS results support the surface migration and ensemble mechanism for carbon formation and give evidence for the reconstruction of the metal particles during the induction period.
Co-reporter:Fang Jin, Ye Tian and Yongdan Li
Industrial & Engineering Chemistry Research 2009 Volume 48(Issue 4) pp:1873-1879
Publication Date(Web):January 8, 2009
DOI:10.1021/ie8014457
An alkaline treatment is employed for tailoring a commercial H-ZSM-5 to produce a catalyst for the synthesis of pyridine and picolines. The most significant consequence of the alkaline treatment was desilication. However, it is accompanied by extraction of aluminum and formation of extra-framework aluminum (Alef) and amorphous alumina. Slit-shaped intracrystaline mesopores and macropores form. Because of the decrease in the Si/Al ratio in the zeolite framework and the formation of Alef and amorphous alumina, the number of strong acid sites decreases and that of weak acid sites increases. The ratio of Lewis acids to Brönsted acids (L/B) also increases. We note that the induced hierarchical pores and the change of acid strength distribution increase the stability of the catalyst, and the increased L/B causes an increase in the initial yield and comparative selectivity for pyridine and a decrease in those properties for 3-picoline. Coking leads to a gradual deactivation and affects product selectivity.
Co-reporter:Ke Zhang, Huiyuan Gao, Zebao Rui, Peng Liu, Yongdan Li and Y. S. Lin
Industrial & Engineering Chemistry Research 2009 Volume 48(Issue 4) pp:1880-1886
Publication Date(Web):January 5, 2009
DOI:10.1021/ie801417w
The effectiveness of intermediate layer to prevent intermetallic diffusion is a key factor for application of Pd membranes on porous stainless steel (PSS) support. In this work, electroless-plated Pd membranes were prepared on PSS disks with two different intermediate layers: in situ oxidized metal oxide and sol−gel derived mesoporous yttria stabilized zirconia (YSZ). A thinner, gastight Pd layer can be formed on PSS support with the YSZ intermediate layer, resulting in a higher hydrogen permeance than Pd membranes on PSS support with the in situ oxidized metal oxide intermediate layer. High temperature permeation and 100-h stability tests showed that both intermediate layers were effective as the diffusion barrier for Pd membranes on PSS supports in the temperature range of 773−873 K. At temperatures above 873 K, only the YSZ intermediate layer is effective in preventing intermetallic diffusion and gives a stable Pd membrane. At the elevated temperatures Pd membranes on PSS support with in situ oxidation layer suffer from a chemical and mechanical stability problem due to reduction of metal oxides in hydrogen atmosphere which results in intermetallic diffusion and possibly weakens the adhesion of the Pd layer on PSS support.
Co-reporter:Dong Zhang, Lihong Zhang, Bin Liang and Yongdan Li
Industrial & Engineering Chemistry Research 2009 Volume 48(Issue 10) pp:5117-5122
Publication Date(Web):April 24, 2009
DOI:10.1021/ie8019664
The effect of acid treatment on the high-temperature oxidation behavior of Fe−Cr−Al alloy has been examined with oxidation tests and various characterization techniques. Acid treatment effectively improves the stability of the alloy in a high-temperature oxidation environment. After the treatment, the alloy oxidizes at a higher rate in the induction period and a lower rate in the subsequent time period. A passivative oxide layer was determined to be better formed during high-temperature oxidation on the surface of the acid-treated alloy, which suppressed further oxidation. It was observed that the oxidation rate of the alloy at high temperature can be described precisely by the Quadakkers equation.
Co-reporter:Qinghua Liu, Ye Tian, Chun Xia, Levi T. Thompson, Bin Liang, Yongdan Li
Journal of Power Sources 2008 Volume 185(Issue 2) pp:1022-1029
Publication Date(Web):1 December 2008
DOI:10.1016/j.jpowsour.2008.08.100
A mathematical model was developed to simulate the performance of a direct carbon fuel cell. The model takes account of the electrochemical reaction dynamics, mass-transfer and the electrode processes. An improved packed bed anode was adopted. Polarization losses for the cell components were examined supposing graphite as the fuel and molten carbonate as the electrolyte. The results indicated that the anode activation polarization was the major potential loss in 923–1023 K. The effects of temperature, anode dimension, and carbon particle size on the cell performance were investigated. The model predicted that the power density can be as high as 200–500 W m−2, with carbon particle size in the range 1.0 × 10−7 to 1.0 × 10−4 m and in 923–1023 K and that the overall efficiency of the cell is higher than 55% for low current density and is 45–50% for high current density.
Co-reporter:Xue Yang ; Zhaofu Fei ; Dongbin Zhao ; Wee Han Ang ; Yongdan Li ;Paul J. Dyson
Inorganic Chemistry 2008 Volume 47(Issue 8) pp:3292-3297
Publication Date(Web):March 14, 2008
DOI:10.1021/ic702305t
Highly stable palladium nanoparticles (Pd NPs), protected by an imidazolium-based ionic polymer (IP) in a functionalized ionic liquid (IL), have been prepared and characterized by transmission electron microscopy (TEM). These Pd NPs are excellent precatalysts for Suzuki, Heck, and Stille coupling reactions and can be stored without undergoing degradation for at least 2 years. The NP−IP−IL system may therefore be considered as an alternative to the traditional palladium on carbon (Pd/C) precatalyst employed in many C−C coupling reactions, also allowing reactions to be conducted under “solvent-free” conditions.
Co-reporter:Shuo Liu, Ke Zhang, Lining Fang and Yongdan Li
Energy & Fuels 2008 Volume 22(Issue 2) pp:1365-1370
Publication Date(Web):January 23, 2008
DOI:10.1021/ef700614d
A thermodynamic analysis of ethanol oxidative steam reforming was carried out with a Gibbs free energy minimization method. The addition of oxygen lowers the enthalpy of the system and favors the heat recycle. Thermal-neutral (TN) conditions are obtained, at which the heat released from exothermic reactions makes up exactly for the requirement of the endothermic reactions. At three temperatures, 700, 900, and 1100 K, the ratios of H2O/EtOH and O2/EtOH for making up TN conditions are estimated, and the equilibrium moles of hydrogen, methane, carbon monoxide, and carbon are examined. 900 K is favorable for hydrogen production where the maximum equilibrium mole of hydrogen appears, with coke and methane being suppressed effectively. For the non-TN operations, a detailed calculation is presented on a range of reaction conditions, i.e., temperature of 700–1100 K and H2O/EtOH and O2/EtOH feed ratios in 1.0–10.0 and 0.0–0.9, respectively. Hydrogen is favored at low O2/EtOH ratio, high H2O/EtOH ratio, and 900 K. Methane is not favored at high temperatures and high O2/EtOH and H2O/EtOH ratios. Carbon monoxide increases with the increase of temperature. Carbon formation can be avoided by adjusting the reaction condition in a reasonable range.
Co-reporter:Zebao Rui, Ke Zhang, Yongdan Li, Y.S. Lin
International Journal of Hydrogen Energy 2008 Volume 33(Issue 9) pp:2246-2253
Publication Date(Web):May 2008
DOI:10.1016/j.ijhydene.2008.02.047
A one-dimensional dense membrane reactor (DMR) model has been developed to simulate the partial oxidation of methane to syngas. A combustion–reforming mechanism was adopted and the oxidation of reforming products, i.e. H2H2 and CO, was considered. The performance of the DMR and a conventional fixed-bed reactor was compared and discussed. The results show that the incorporation of the product oxidation steps has a significant effect on the simulation results of a DMR and provides a reasonable explanation of the experimental data. The model is therefore more reasonable than those ignoring the product oxidation reactions.
Co-reporter:Zebao Rui, Ke Zhang, Yongdan Li, Y.S. Lin
International Journal of Hydrogen Energy 2008 Volume 33(Issue 10) pp:2501-2506
Publication Date(Web):May 2008
DOI:10.1016/j.ijhydene.2008.02.073
A one-dimensional non-isothermal model was employed in the simulation of partial oxidation of methane to syngas in a dense oxygen permeation membrane reactor. The model predicts that if methane is consumed completely in the reactor, a temperature runaway occurs. The reactor inlet temperature is chosen as a major factor to demonstrate the correlativity of the reactor performance and this phenomenon. A borderline inlet temperature (BIT) is defined. Simulation results showed that when the reactor inlet temperature approaches this value, an optimized reactor performance is achieved. This temperature increases with the increase of the air flow rate and carbon space velocity. The surface exchange kinetics at the oxygen-rich side has a small effect on this temperature, while that at the oxygen-lean side has a significant effect.
Co-reporter:Haijuan Zhang, Yongdan Li
Powder Technology 2008 Volume 183(Issue 1) pp:73-78
Publication Date(Web):18 March 2008
DOI:10.1016/j.powtec.2007.11.013
A Beta/MCM-41 composite zeolite with a stepwise-distributed pore structure was prepared with a silica-alumina source originated from alkaline treatment of zeolite Beta. The material was characterized by various techniques. The results indicated that this composite possesses a mesopore system of MCM-41 and the microporous structure of Beta zeolite. Hydrothermal stability and acidity was improved over MCM-41 due to the introduction of Beta building units into the mesopore walls. The composite was used as the support of a Pd-Pt catalyst for the hydrogenation of naphthalene in the presence and absence of 4, 6-dimethyldibenzothiophene. It was demonstrated that the catalyst has an enhanced activity and sulfur tolerance during naphthalene hydrogenation.In an attempt to design a family of sulfur-tolerant noble catalysts, a stepwise-distributed pore structure Beta/MCM-41 composite was prepared with a silica-alumina source originated from alkaline treatment of zeolite Beta. This approach takes the advantages of meso and micro-pore structures, shape selectivity and hydrogen spillover effects, and the diffusion barrier is minimized.
Co-reporter:Xue Yang ; Zhaofu Fei ; Tilmann J. Geldbach ; Andrew D. Phillips ; Christian G. Hartinger ; Yongdan Li ;Paul J. Dyson
Organometallics 2008 Volume 27(Issue 15) pp:3971-3977
Publication Date(Web):July 8, 2008
DOI:10.1021/om800355g
Imidazolium- and pyridinium-based ionic liquids with ether/polyether substituents have been evaluated as solvents for palladium-catalyzed Suzuki C−C coupling reactions. In general, reactions proceed more efficiently in these solvents compared to other ionic liquids, which is believed to be due to better stabilization of the palladium catalyst, involving weak interactions with the ether groups. The position and the number of oxygen atoms in the ether side chain strongly influence the outcome of the coupling reactions in the imidazolium-based ionic liquids, whereas for the pyridinium-based liquids no influence is observed. Carbene derivatives, generated from the imidazolium-based ionic liquids, are believed to play a role by terminating the catalytic cycle, and representative species have been isolated and characterized from stoichiometric reactions.
Co-reporter:Yongdan Li, Dongfang Wu, Jianpo Zhang, Liu Chang, Dihua Wu, Zhiping Fang, Yahua Shi
Powder Technology 2000 Volume 113(1–2) pp:176-184
Publication Date(Web):20 November 2000
DOI:10.1016/S0032-5910(00)00231-X
Mechanical-strength measurement methods for differently shaped solid catalysts, such as crushing, knife-edge cutting and three-point bending have been discussed. The strength data were correlated by Weibull distribution. Experimental results show that, except for the crushing strength test on extruded catalysts, all strength tests have a single fracture mode, and the strength failures are due to brittle fracture, originating from tensile stress concentration at the edges of the existing flaws in the catalyst pellets. The suitability of different test methods for spheres, tablets and extrudates, respectively, are discussed. It is concluded that the crushing test is a satisfactory method for spheres, and crushing and cutting tests are both suitable for tablets, while cutting and bending tests are appropriate for extrudates.
Co-reporter:Lei Zhang, Wenqian Fu, Quanyong Yu, Tiandi Tang, Yicheng Zhao, Yongdan Li
Journal of Catalysis (January 2017) Volume 345() pp:295-307
Publication Date(Web):1 January 2017
DOI:10.1016/j.jcat.2016.11.019
•Small and highly dispersed Ni2P nanoparticles on MZSM-5 were prepared by adding citric acid (CA).•The mechanism of formation of small Ni2P particles with CA assistance was investigated.•Small Ni2P particles on MZSM-5 exhibit high hydrogenation activity.Preparing small, highly dispersed Ni2P particles is important for improving the hydrogenation ability of Ni2P. Here, Ni2P nanoparticles (approximately 4.3 nm) on mesoporous zeolite ZSM-5 (Ni2P/MZSM-5-CA) were prepared using citric acid (CA) as an assistant agent. The formation mechanism of small Ni2P particles when CA was added was investigated by combining UV–vis diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy, and temperature-programmed reduction with a transmission electron microscope and CO chemisorption. The results indicated that the formed CA–Ni complex with high viscosity favors the Ni precursor dispersed on the dried catalyst. After calcination, the released Ni species strongly interacted with surface acidic hydroxyl groups on MZSM-5, leading to the formation of Ni2P particles with small sizes and good dispersion under a reducing atmosphere. The reaction rate constants and TOFs over Ni2P/MZSM-5-CA (16.2 × 10−2 μmol g−1 s−1 and 9.7 × 10−4 s−1) are much higher than over Ni2P/MZSM-5 (8.2 × 10−2 μmol g−1 s−1 and 8.3 × 10−4 s−1) in 4,6-dimethyldibenzothiophene hydrodesulfurization. In addition, Ni2P/MZSM-5-CA catalyst shows higher activity than Ni2P catalyst without CA in phenanthrene hydrogenation.Download high-res image (213KB)Download full-size image
Co-reporter:Zebao Rui, Yongdan Li, Y.S. Lin
Chemical Engineering Science (January 2009) Volume 64(Issue 1) pp:172-179
Publication Date(Web):1 January 2009
DOI:10.1016/j.ces.2008.09.022
The oxygen permeation through oxygen ionic or mixed-conducting ceramic membranes under reaction conditions was examined with a model taking into account of different electrical transport mechanisms (p-type and n-type transports) and finite reaction rate. It was demonstrated that with a reaction consuming oxygen in one side of the membrane, the oxygen partial pressure in the reaction side decreases and the oxygen permeation flux increases with the increase in the reaction rate for both the p-type and the n-type transport dominated mechanism. The increase in reaction rate causes a transition of the transport mechanism from p-type to n-type. This transition leads to an increase in the permeation flux by up to 30 times. This effect offers one explanation for the large discrepancies in published permeation data for membrane reactors of partial oxidation reaction employing an oxygen permeable dense ceramic membrane. For a membrane with a specific transport mechanism, the increase in the reactant partial pressure causes an increase in the reaction rate and oxygen permeation flux. However, the increase in the inlet inert gas amount has a complicated effect on the oxygen permeation flux because it lowers both oxygen partial pressure and the reaction rate at the same time.
Co-reporter:Jingran Xiao, Xuelan Hou, Le Zhao, Yongdan Li
Journal of Catalysis (February 2017) Volume 346() pp:70-77
Publication Date(Web):1 February 2017
DOI:10.1016/j.jcat.2016.11.028
•The CQDs@ZnO:Ga/ZnO composite combines type I and type II n–n heterojunctions.•CQD sensitization can eliminate the energy barrier at the type I ZnO:Ga/ZnO junction.•CQDs@ZnO:Ga/ZnO gives a negatively shifted onset potential.•The CQDs@ZnO:Ga/ZnO photoanode exhibits remarkably enhanced PEC performance.•The CQDs@ZnO:Ga/ZnO composite shows better photostability.A carbon quantum dot (CQD)-sensitized ZnO:Ga/ZnO composite photoanode for photoelectrochemical water splitting has been designed and tested. In the composite, a ZnO array is grown on a piece of indium tin oxide glass and facilitates the essential integrity of the photoanode. An overlayer of Ga–doped ZnO (ZnO:Ga) is then hydrothermally grown on the ZnO nanorods. A type I ZnO:Ga/ZnO junction forms with a ZnO:Ga shell possessing visible light activity and a narrow bandgap. However, a highly positive onset potential exists due to the location of the conduction band (CB) of ZnO:Ga at the high end. The deposition of the CQDs on the surface of the overlayer provides a negatively shifted CB with a type II junction between ZnO:Ga and CQDs. The CQDs@ZnO:Ga/ZnO multijunction composite photoanode exhibits a negative shift of the onset potential and a significantly increased photocurrent density, up to 1.5 mA cm−2 at 1.6 V vs. RHE, with good photostability under AM 1.5 G simulated light. The multijunction composite photoanode also achieves a current density of 0.16 mA cm−2 under visible light at a bias of 1.0 V, which is comparable to that of ZnO under AM 1.5 G simulated light. Electrochemical impedance spectra reveal that the CQD modification acts to decrease the interfacial charge transfer resistance associated with eliminating the energy barrier in the type I ZnO:Ga/ZnO junction that causes charge transfer resistance.Download high-res image (95KB)Download full-size image
Co-reporter:Yang Li, Xiaoli Zhang, Shaohong Jiang, Yongdan Li
Journal of Catalysis (December 2014) Volume 320() pp:208-214
Publication Date(Web):1 December 2014
DOI:10.1016/j.jcat.2014.10.002
•An auto-catalytic material In–Ni–Ta–O–N is synthesized via solid-state reaction.•The In–Ni–Ta–O–N can produce NiOOH as an O2 evolution site on its surface.•The In–Ni–Ta–O–N can split water into stoichiometric H2 and O2 under sunlight.•The In–Ni–Ta–O–N is an n-type semiconductor with an Fermi level around 0.3 V.•The In–Ni–Ta–O–N has perfect band edges for the overall water splitting.A mixed oxynitride, with the formula In–Ni–Ta–O–N, has been examined and used in the preparation of photoelectrodes for water splitting. The material belongs to a monoclinic crystal system and has a layered structure. The nitrogen content is determined by a thermogravimetric method. The flat band of the material is determined with a Mott–Schottky plot and is located at +0.3 V vs. RHE. Cyclic voltammograms and XPS spectra prove that the material catalyzes a self-transformation, forming NiOOH at the surface, which acts as the active oxygen evolution site. Under simulated sunlight, the material exhibits stable hydrogen (62.4 μmol h−1 g−1) and oxygen (29.6 μmol h−1 g−1) evolution rates from water without any sacrificial reagent and without any additional co-catalyst. The open-circuit photovoltage measurement indicates that the low concentration of photogenerated charge carriers limits the performance of the material as a photoelectrode. Furthermore, two different sacrificial reagents are applied to show that the hydrogen evolution reaction is the rate-determining step in water splitting under visible light.Download high-res image (206KB)Download full-size image
Co-reporter:Xiaolei Ma, Ye Tian, Wenyue Hao, Rui Ma, Yongdan Li
Applied Catalysis A: General (5 July 2014) Volume 481() pp:64-70
Publication Date(Web):5 July 2014
DOI:10.1016/j.apcata.2014.05.002
Co-reporter:Hong Chen, Xinli Tong, Yongdan Li
Applied Catalysis A: General (30 November 2009) Volume 370(Issues 1–2) pp:59-65
Publication Date(Web):30 November 2009
DOI:10.1016/j.apcata.2009.09.017
Co-reporter:Yongdan Li, Douxing Li, Gaowei Wang
Catalysis Today (29 March 2011) Volume 162(Issue 1) pp:1-48
Publication Date(Web):29 March 2011
DOI:10.1016/j.cattod.2010.12.042
Methane catalytic decomposition is a promising process that simultaneously produces COx-free hydrogen and carbon nanomaterial. The hydrogen produced can be consumed directly by proton exchange membrane fuel cell (PEMFC), while the carbon can be used as the fuel of direct carbon fuel cell (DCFC) and as the components of advanced materials. The recent advances in the reaction mechanism and kinetics on group 8–10 base metal catalysts are reviewed. Special attention is paid to the roles of metal particles and the deactivation mechanism of the catalyst during the reaction. The performances of the often used catalysts are summarized and the effects of the promoters, supports and preparation techniques are outlined. The kinetic models derived from different mechanism and the empirical correlations are compared. The process characteristics, such as the origin of the trace amount of CO in the product, the process factors influencing CO formation and the overall catalyst productivity are discussed. Processes based on the topic reaction and their applications are introduced.Graphical abstractDownload high-res image (149KB)Download full-size imageResearch highlights► Methane catalytic decomposition reaction produces COx-free hydrogen and carbon nanomaterial. ► The recent advances in the research on the reaction mechanism and kinetics on group 8–10 base metal catalysts are reviewed. ► The catalysts and its preparation techniques are outlined. ► The processes based on the topic reaction and their applications are introduced. ► A high efficiency energy conversion system can be built with a methane decomposition reactor, a direct carbon fuel cell and a proton exchange membrane fuel cell.
Co-reporter:Xinli Tong, Mengran Li, Ning Yan, Yang Ma, Paul J. Dyson, Yongdan Li
Catalysis Today (25 October 2011) Volume 175(Issue 1) pp:524-527
Publication Date(Web):25 October 2011
DOI:10.1016/j.cattod.2011.03.003
A highly efficient iron-catalyzed production of 5-hydroxymethylfurfural (HMF) from sugar is reported. The dehydration of fructose and sucrose has been studied in the presence of different iron salts and co-catalysts. As a result, it was found that fructose and sucrose could be efficiently and selectively converted to HMF using a combination of environmentally friendly FeCl3 and tetraethyl ammonium bromide (Et4NBr) as the catalytic system. For instance, 86% HMF yield at full conversion of fructose was obtained for 2 h at 90 °C in air. The effects of catalyst concentration, reaction time and reaction temperature were investigated in detail. The electronic absorption spectra of different catalysts were recorded, and the FeCl3Br− ion was considered as the active catalyst species.Graphical abstract.Download high-res image (127KB)Download full-size imageHighlights► Efficient defunctionalization of fructose and sucrose is achieved. ► Catalytic system includes FeCl3 and tetraethyl ammonium bromide. ► Hydroxymethylfurfural is produced from fructose and sucrose. ► The catalyst active species is discussed.
Co-reporter:Fang Jin, Yugang Cui, Yongdan Li
Applied Catalysis A: General (15 November 2008) Volume 350(Issue 1) pp:71-78
Publication Date(Web):15 November 2008
DOI:10.1016/j.apcata.2008.07.041
Co-reporter:Hong Chen, Jihui Wang, He Li, Dongfang Wu, Mingfa Yao, Yongdan Li
Applied Catalysis A: General (15 June 2012) Volumes 427–428() pp:73-78
Publication Date(Web):15 June 2012
DOI:10.1016/j.apcata.2012.03.035
Co-reporter:Fang Jin, Yongdan Li
Catalysis Today (15 July 2009) Volume 145(Issues 1–2) pp:101-107
Publication Date(Web):15 July 2009
DOI:10.1016/j.cattod.2008.06.007
The amount, type, origin and strength distribution of acid sites on ZSM-5 zeolite were analyzed with pyridine as a probe molecule, and with the aid of FTIR and interrupted-temperature programmed desorption techniques. Desorption activation energy (DAE) was used as a measure of the acid strength. The acid sites were divided into four sets each with a mean strength of DAE 70, 90, 120 and 150 kJ mol−1. Brönsted (B) sites were found dominant in the set with DAE 150 kJ mol−1, while Lewis (L) sites prevail for the DAE 120 kJ mol−1 set. For the other two sets both B and L sites are important. The B sites with DAE 70 kJ mol−1 were attributed to terminal silanol groups, and the B sites with DAE 90 kJ mol−1 were due to bridged hydroxyl and extraframework AlOH groups.
Co-reporter:Guangming Zeng, Qinghua Liu, Ruixue Gu, Lihong Zhang, Yongdan Li
Catalysis Today (15 December 2011) Volume 178(Issue 1) pp:206-213
Publication Date(Web):15 December 2011
DOI:10.1016/j.cattod.2011.07.036
Nickel based mixed oxide catalysts derived from Ni–Mg–Zn–Al hydrotalcite-like precursors are prepared and evaluated for H2-rich gas production via ethanol steam reforming. It has been found that the catalyst properties (e.g. BET surface area, Ni dispersion and reducibility) and catalytic performance depend on the Mg:Zn molar ratio. MgO and ZnO have a synergetic effect. At 700 °C, the quaternary catalyst with a Mg:Zn ratio of 4 exhibits the highest H2 yield and best stability, viz. no apparent variation of the product distribution over 100 h operation, whereas the ternary catalyst without Mg suffers severe coke accumulation after 7 h on-stream. Two types of carbon (filamentous and amorphous) are found deposited on the catalyst surface. The carbon deposited is dominated by filamentous carbon, which is likely originated from the decomposition of methane, and does not cause immediate deactivation.Graphical abstractLong-term stability test over a catalyst with Mg:Zn ratio = 4 at 700 °C.Download high-res image (94KB)Download full-size imageHighlights► Ni/Mg–Zn–Al catalysts derived from hydrotalcite-like precursors are active in ethanol steam reforming. ► The quaternary catalyst with a Mg:Zn ratio of 4 is hard to reduce, has a high Ni dispersion and good catalytic performance. ► TPO and HR-TEM verify that two types of carbon deposited on the catalyst surface.
Co-reporter:Rui Ma, Kai Cui, Le Yang, Xiaolei Ma and Yongdan Li
Chemical Communications 2015 - vol. 51(Issue 51) pp:NaN10301-10301
Publication Date(Web):2015/05/14
DOI:10.1039/C5CC01900A
An activated carbon supported α-molybdenum carbide catalyst (α-MoC1−x/AC) showed remarkable activity in the selective deoxygenation of guaiacol to substituted mono-phenols in low carbon number alcohol solvents. Combined selectivities of up to 85% for phenol and alkylphenols were obtained at 340 °C for α-MoC1−x/AC at 87% conversion in supercritical ethanol. The reaction occurs via consecutive demethylation followed by a dehydroxylation route instead of a direct demethoxygenation pathway.
