Co-reporter:Hai-Sheng Lu, Haimin Zhang, Rongrong Liu, Xian Zhang, Huijun Zhao, Guozhong Wang
Applied Surface Science 2017 Volume 392() pp:402-409
Publication Date(Web):15 January 2017
DOI:10.1016/j.apsusc.2016.09.045
Highlights
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Macroscale Co-MOFs crystals are synthesized by a facile solvothermal reaction.
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Co@NPCsamplesarepreparedthroughdirectpyrolysisofCo-MOFscrystals.
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Co@NPC-900 and Co@NPC-1000 exhibit bifunctional electrocatalytic activities of both ORR and OER.
Co-reporter:Yanping Su;Chun Chen;Xiaoguang Zhu;Yong Zhang;Wanbing Gong;Haimin Zhang;Huijun Zhao
Dalton Transactions 2017 vol. 46(Issue 19) pp:6358-6365
Publication Date(Web):2017/05/15
DOI:10.1039/C7DT00628D
We report a fast and simple method for the synthesis of Ni-based metal–organic-frameworks (Ni-MOFs). Due to the existence of nickel ions and an organic ligand, the MOFs are employed as a sacrificial template for the facile preparation of carbon-embedded Ni (Ni/C) catalysts by a direct thermal decomposition method. The obtained Ni/C catalysts exhibit excellent catalytic activity for selectively transforming furfural (FAL) to tetrahydrofurfuryl alcohol (THFOL) due to the Ni nanoparticles (NPs) embedded uniformly in the ligand-derived carbon. The exemplified results illustrate that the catalytic performance of the Ni/C catalyst is greatly affected by the calcination conditions (temperature and time), composition of the Ni-MOF precursor and the catalysis conditions. The conversion of FAL and selectivity of THFOL both reached 100% under the conditions of 120 °C, 1 MPa H2 pressure and 120 min of hydrogenation over the Ni/C-500 catalyst, derived from the pyrolysis of Ni-MOFs (Ni : BTC mole ratio of 1.0) at 500 °C for 120 min, which exhibits an average nanoparticle size of ∼14 nm and uniform dispersion, and the highest BET surface area (∼92 m2 g−1) among all investigated Ni/C catalysts. This facilely prepared heterogeneous catalyst would be very promising for the replacement of noble metal catalysts for the efficient catalytic conversion of biomass-derived feedstocks into value-added chemicals.
Co-reporter:Rongrong Liu;Haimin Zhang;Xian Zhang;Tianxing Wu;Huijun Zhao
RSC Advances (2011-Present) 2017 vol. 7(Issue 31) pp:19181-19188
Publication Date(Web):2017/03/28
DOI:10.1039/C7RA01798G
In this study, we first synthesized Co9S8@N-doped porous carbon (Co9S8@NC) using shrimp-shell derived carbon nanodots as a carbon/nitrogen source in the presence of CoSO4 by a one-step molten-salt calcination method. This was followed by low-temperature phosphorization in the presence of NaH2PO2, whereby Co9S8@N,P-doped porous carbon (Co9S8@NPC) was finally obtained using the Co9S8@NC as a precursor. The results demonstrated that the molten-salt calcination approach can effectively create a pyrolytic product with a porous structure and improve the material’s surface area, which is favourable for electrocatalysis-related mass transport and the exposure of catalytic active sites during electrocatalysis. As an electrocatalyst, Co9S8@NPC exhibits higher catalytic activity for the hydrogen evolution reaction (HER) than Co9S8@NC in an alkaline medium. Among all the investigated Co9S8@NPC catalysts, Co9S8@NPC-10 (mass ratio of NaH2PO2 to Co9S8@NC = 10 : 1) displays the best HER activity with an overpotential of 261 mV at 10 mA cm−2 in the alkaline medium. Interestingly, Co9S8@NPC-10 also displays good catalytic activity for the oxygen evolution reaction (OER) in this study. Owing to its bifunctional catalytic activity towards the HER and OER, the fabricated Co9S8@NPC-10 was simultaneously used as an anode and cathode material to generate O2 and H2 from overall water splitting in the alkaline medium, exhibiting a nearly 100% faradaic yield. This study would be helpful to the design and development of high performance non-precious metal electrocatalysts to be applied in overall water splitting to produce H2 and O2.
Co-reporter:Tianxing Wu;Yunxia Zhang;Mingguang Kong;Huijun Zhao
New Journal of Chemistry (1998-Present) 2017 vol. 41(Issue 18) pp:10305-10311
Publication Date(Web):2017/09/11
DOI:10.1039/C7NJ02007D
A diffusive gradients in thin films technique (DGT) device using thiol-modified carbon nanoparticle (SH-CNP) suspension as the liquid binding phase and cellulose acetate membrane as the diffusive layer was evaluated for determination of Hg2+ in water. Laboratory DGT validation experiments gave linear mass uptake over time (R2 ≥ 0.99) for Hg2+ in solutions of different concentrations. The effect of pH, ionic strength and potential interfering ions on Hg2+ binding with DGT devices was investigated. The results showed that the gathering amount of SH-CNPs-DGT for Hg2+ reached the maximum when the pH of solution was close to neutral and the ionic strength of solution and co-existing potential interfering ions such as Cd2+, Cr3+, Cu2+ and Pb2+ had no significant effect on gathering of SH-CNPs-DGT for Hg2+. Finally, validation of the SH-CNPs-DGT devices was undertaken for Hg2+ in spiked local water systems (Dongpu Reservoir and Nanfei River). For in situ measurements in Nanfei River water, the average labile Hg concentrations were 0.091 ± 0.009, 0.053 ± 0.003, and 0.071 ± 0.006 μg L−1 for three, six and seven days, respectively, which were lower than the value obtained by using ICP-MS, as DGT only measures ionic mercury and labile mercury species but direct measurement measures total mercury including inert organic species and large colloids.
Co-reporter:Fengchao Su, Hongjian Zhou, Yunxia Zhang, Guozhong Wang
Journal of Colloid and Interface Science 2016 Volume 478() pp:421-429
Publication Date(Web):15 September 2016
DOI:10.1016/j.jcis.2016.06.035
A facile freeze-drying method was presented to fabricate three dimensional (3D) honeycomb-like structured nanoscale zero-valent iron/chitosan composite foams (ICCFs) for effective removal of inorganic arsenic in water. It was found that freezing temperature has important influence on the formation of 3D network structure of ICCFs. The ICCFs obtained at freeze temperature of −80 °C exhibits oriented porous structure with good mechanical property than that at −20 °C, thus improved excellent removal capability of As(III) and As(V) up to 114.9 mg g−1 and 86.87 mg g−1, respectively. Further, the adsorption kinetics of ICCFs on As(III) and As(V) can be described by pseudo-second order model and their adsorption isotherms follow Langmuir adsorption model. The superior removal performance of ICCFs on As(III) and As(V) can be ascribed to its oriented porous structure with abundant adsorption active sites resulted from nZVI and O, N-containing functional groups in ICCFs. Importantly, it was found that the O, N-containing functional groups of chitosan in ICCFs can adequately bind with the dissolved Fe3+ ions from oxidation of nZVI to form Fe3+-Chitosan complex during removal of As(III) and As(V), thus effectively avoiding the dissolved Fe3+ ions into solution to produce secondary pollution. A possible adsorption-coupled reduction mechanism of ICCFs on As(III) and As(V) was also proposed based on the experimental results. We believe that this work would be helpful to develop low-cost and abundant chitosan-based materials as high performance adsorbents for environmental remediation applications.The three dimensional honeycomb-like structured nanoscale zero-valent iron/chitosan composite foams were fabricated by a facile the freeze-drying method and exhibited excellent removal capability to As(III) and As(V) and avoided the secondary pollution of nanoscale zero-valent iron related species.
Co-reporter:Nannan Qin, Ya Zhang, Hongjian Zhou, Zhigang Geng, Gang Liu, Yunxia Zhang, Huijun Zhao, Guozhong Wang
Journal of Colloid and Interface Science 2016 Volume 472() pp:8-15
Publication Date(Web):15 June 2016
DOI:10.1016/j.jcis.2016.03.025
The reactivity of zero valent iron (Fe0) for removing Cr(VI) is self-inhibiting under neutral and alkaline conditions, due to the precipitation of ferrous hydroxide on the surface of Fe0. To overcome this difficulty, we incorporated a second metal (Co) into Fe0 to form FeCo bimetallic nanoparticles (FeCo BNPs), which can achieve higher activity and significant improvement in the reaction kinetics for the removal of Cr(VI) compared with Fe0. The FeCo BNPs were synthesized by a hydrothermal reduction method without using any templates. The characterization analysis indicated that the products were highly uniform in large scale with 120–140 nm size in diameter. The obtained FeCo BNPs exhibited a remarkable removal ability for Cr(VI) in the pH range of 5.3–10.0. Especially, FeCo BNPs were able to reduce trace Cr(VI) (1.0 mg L−1, pH = 7.5) down to about 0.025 mg L−1 within 1 h. XPS analysis confirmed that Cr(VI) was reduced to Cr(III) by FeCo BNPs, while Fe and Co was oxidized, implying a chemical reduction process. The enhanced removal of trace Cr(VI) could be originated from the introduction of Co, which not only served as a protecting agent against surface corrosion by galvanic cell effect, but also enhanced the efficient flow of electron transfer between iron and Cr(VI). All the results primarily imply that FeCo BNPs can be employed as high efficient material for wastewater treatment.FeCo bimetallic nanoparticles were synthesized by a hydrothermal reduction method for removing trace Cr(VI) from neutral and alkaline aqueous solution under a synergistic adsorption and chemical reduction process.
Co-reporter:Rongrong Liu, Haimin Zhang, Shengwen Liu, Xian Zhang, Tianxing Wu, Xiao Ge, Yipeng Zang, Huijun Zhao and Guozhong Wang
Physical Chemistry Chemical Physics 2016 vol. 18(Issue 5) pp:4095-4101
Publication Date(Web):07 Jan 2016
DOI:10.1039/C5CP06970J
Development of cheap, abundant and metal-free N-doped carbon materials as high efficiency oxygen reduction electrocatalysts is crucial for their practical applications in future fuel cell devices. Here, three-dimensional (3D) N-doped porous carbon (NPC) materials have been successfully developed by a simple template-assisted (e.g., SiO2 spheres) high temperature pyrolysis approach using shrimp-shell derived N-doped carbon nanodots (N-CNs) as carbon and nitrogen sources obtained through a facile hydrothermal method. The shrimp-shell derived N-CNs with a product yield of ∼5% possess rich surface O- and N-containing functional groups and small nanodot sizes of 1.5–5.0 nm, which are mixed with surface acidification treated SiO2 spheres with an average diameter of ∼200 nm in aqueous solution to form a N-CNs@SiO2 composite subjected to a thermal evaporation treatment. The resultant N-CNs@SiO2 composite is further thermally treated in a N2 atmosphere at different pyrolysis temperatures, followed by acid etching, to obtain 3D N-doped porous carbon (NPC) materials. As electrocatalysts for oxygen reduction reaction (ORR) in alkaline media, the experimental results demonstrate that 3D NPC obtained at 800 °C (NPC-800) with a surface area of 360.2 m2 g−1 exhibits the best ORR catalytic activity with an onset potential of −0.06 V, a half wave potential of −0.21 V and a large limiting current density of 5.3 mA cm−2 (at −0.4 V, vs. Ag/AgCl) among all NPC materials investigated, comparable to that of the commercial Pt/C catalyst with an onset potential of −0.03 V, a half wave potential of −0.17 V and a limiting current density of 5.5 mA cm−2 at −0.4 V. Such a 3D porous carbon ORR electrocatalyst also displays superior durability and high methanol tolerance in alkaline media, apparently better than the commercial Pt/C catalyst. The findings of this work would be valuable for the development of low-cost and abundant N-doped carbon materials from biomass as high performance metal-free electrocatalysts.
Co-reporter:Honglin Yao, Qianqian Ding, Hongjian Zhou, Zhenfu Zhao, Gang Liu and Guozhong Wang
RSC Advances 2016 vol. 6(Issue 32) pp:27039-27046
Publication Date(Web):02 Mar 2016
DOI:10.1039/C6RA03172B
In this study, mesoporous amino-group functionalised iron/silica hollow spheres (Fe/SiO2–NH2 HSs) were successfully developed as a magnetic absorbent for the highly effective removal of Cr(VI) ions. The Fe/SiO2–NH2 HSs were synthesized using monodispersed silica colloids as a chemical template, followed by a one-pot hydrothermal treatment, hydrogen reduction and surface modification with an amino silane coupling agent. The Fe/SiO2–NH2 HSs have a diameter of ca. 950 nm and a shell thickness of ca. 60 nm, and the surfaces were composed of Fe and SiO2 units with amino functional groups. Meanwhile, the ferromagnetic property endowed them with easy recyclability for practical applications. The Fe/SiO2–NH2 HSs exhibited significantly improved ability to remove pollutant Cr(VI) and methyl orange. The removal percentage of Cr(VI) (8 mg L−1) could reach 98.3% in just 5 min using Fe/SiO2–NH2 HSs; however, only 10% of Cr(VI) were removed using the unmodified samples. XPS analysis suggested that the removal of Cr(VI) was attributed to the adsorption and reduction synergistic process of the Fe/SiO2–NH2 HSs. During the process, an electrostatic attraction occurred between the positively charged amino-groups and the negatively charged pollutant species in the aqueous solution, and adsorbed Cr(VI) ions were reduced to Cr(III) species by the iron of Fe/SiO2–NH2 HSs.
Co-reporter:Anle Dong;Xinxin Ye;Hongying Li;Yunxia Zhang
Journal of Soils and Sediments 2016 Volume 16( Issue 8) pp:2030-2040
Publication Date(Web):2016 August
DOI:10.1007/s11368-016-1396-3
The presence of high copper (Cu) and cadmium (Cd) contamination in soils around mining areas has raised serious health concerns. Improving hydroxyapatite (HAP) adsorption capacity for Cu and Cd is important if its application potential in heavily contaminated soils is to expand.The micro/nanostructured HAP (mnHAP) was synthesized using a template-induced method to improve the HAP immobilization of Cu and Cd in contaminated soils. Commercial and synthetic HAPs were evaluated as amendments in Cu and Cd remediation tests with 1.5 and 3.0 % addition level for 90 days, and soils without HAP materials (0.0 %) were designated as the controls; each treatment was repeated three times. The materials were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), N2 adsorption, and scanning electron microscopy (SEM)-energy-dispersive spectra (EDS) and then quantitatively determined the Cu and Cd contents by inductively coupled plasma (ICP) and inductively coupled plasma mass spectrometry (ICP-MS).The mnHAP was more effective in immobilizing Cu and Cd than the two commercial HAPs. After treatment with mnHAP at the 3.0 % addition level for 90 days, the contaminated soils showed 55.2 and 84.8 % reductions in Cu and Cd concentrations in the toxicity characteristic leaching procedure (TCLP) leaching procedure, respectively. The experimental data indicated that the enhanced Cu and Cd immobilization by mnHAP was due to the increases of surface area and the improvement of structure and newly introduced carboxylate groups on its surface.These findings show that regulating the structure and surface properties of HAP can enhance Cu and Cd immobilization in soils.
Co-reporter:Tianxing Wu;Xiaoguang Zhu;Porun Liu;Xian Zhang
Nano Research 2016 Volume 9( Issue 3) pp:745-754
Publication Date(Web):2016 March
DOI:10.1007/s12274-015-0953-1
A chitosan-polyvinyl alcohol (CS/PVA) co-polymer substrate possessing a large number of amino and hydroxyl groups is used as a substrate to induce the direct growth and in situ sequential transformation of titanate crystals under HF vapor phase hydrothermal conditions. The process involves four distinct formation/transformation stages. HTiOF3 crystals with well-defined hexagonal shapes are formed during stage I, and are subsequently transformed into {001} faceted anatase TiO2 crystal nanosheets during stage II. Interestingly, the formed anatase TiO2 crystals are further transformed into cross-shaped and hollow squareshaped HTiOF3 crystals during stages III and IV, respectively. Although TiO2 crystal phases and facet transformations under hydrothermal conditions have been previously reported, in situ crystal transformations between different titanate compounds have not been widely reported. Such crystal formation/transformations are likely due to the presence of large numbers of amino groups in the CS/PVA substrate. When celluloses possessing only hydroxyl groups are used as a substrate, the direct formation of {001} faceted TiO2 nanocrystal sheets is observed (rather than any sequential crystal transformations). This substrate organic functional group-induced crystal formation/transformation approach could be applicable to other material systems.
Co-reporter:Zhigang Geng, Haimin Zhang, Qizhong Xiong, Yunxia Zhang, Huijun Zhao and Guozhong Wang
Journal of Materials Chemistry A 2015 vol. 3(Issue 38) pp:19455-19460
Publication Date(Web):20 Aug 2015
DOI:10.1039/C5TA05610A
In this work, a three-dimensional (3D) chitosan hydrogel with superior fluorescence properties was successfully fabricated by modifying chitosan fibers with glutaric dialdehyde (GD) via a simple cross-linking approach. The resulting three-dimensional fluorescent chitosan hydrogel (3D-FCH) with hydrophilic properties exhibited a strong blue fluorescence emission at an excitation wavelength of 337 nm. The fluorescence mechanism of the as-synthesized 3D-FCH was investigated and proposed in detail using X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR) techniques. As a solid-phase fluorescent probe, the 3D-FCH was used to selectively and sensitively determine mercury(II) (Hg2+) ions in aqueous media. The results demonstrated that a prominent fluorescence quenching at 401 nm was observed in the presence of Hg2+ with a linear response range of 5.0–50 nM and an estimated limit of detection of 0.9 nM. The fluorescence quenching mechanism could be ascribed to the strong complexation between Hg2+ and the GD fluorophore with a conjugate structure. Moreover, the porous structure of the chitosan hydrogel and the high adsorption capacity of the chitosan fibers in the hydrogel could be very favorable for the rapid fluorescence determination of Hg2+. This work may pave a new way to develop low-cost fluorescent chitosan hydrogels as solid-phase fluorescence determination platforms to replace traditional liquid-phase fluorophores for application in the fluorescence detection of heavy metal ions.
Co-reporter:T. X. Wu, G. Z. Wang, X. Zhang, C. Chen, Y. X. Zhang and H. J. Zhao
Chemical Communications 2015 vol. 51(Issue 7) pp:1334-1337
Publication Date(Web):27 Nov 2014
DOI:10.1039/C4CC09355K
Chitosan, the only alkaline polysaccharide in nature with rich nitrogen content, is used as the sole precursor to obtain N-doped graphitic carbon-based ORR electrocatalysts. The findings of this work demonstrate that cheap, plentiful and renewable biomasses can be transformed into high value functional carbon materials.
Co-reporter:Tianxing Wu, Haimin Zhang, Xian Zhang, Yunxia Zhang, Huijun Zhao and Guozhong Wang
Physical Chemistry Chemical Physics 2015 vol. 17(Issue 41) pp:27527-27533
Publication Date(Web):15 Sep 2015
DOI:10.1039/C5CP04252F
In this work, chitosan whiskers (CWs) were first extracted using low-cost and earth-abundant crab shells as materials by a series of chemical processes, and then assembled into chitosan whisker microspheres (CWMs) via a simple photochemical polymerization approach. Subsequently, a cementite (Fe3C) nanocrystal@N-doped graphitic carbon (Fe3C@NGC) nanocomposite was successfully fabricated by high temperature pyrolysis of CWMs adsorbed with ferric acetylacetonate (Fe(acac)3) at 900 °C. It was found that a suitable growth atmosphere generated inside CWMs during high temperature pyrolysis is critically important to form Fe3C nanocrystal cores, concurrently accompanying a structural transformation from chitosan whiskers to mesoporous graphitic carbon shells with natural nitrogen (N) doping properties, resulting in the formation of a core–shell structure Fe3C@NGC nanocomposite. The resulting samples were evaluated as electrocatalysts for oxygen reduction reaction (ORR). In comparison with sole N-doped graphitic carbon without Fe3C nanocrystals obtained by direct pyrolysis of chitosan whisker microspheres at 900 °C (CWMs-900), Fe3C@NGC showed significantly improved ORR catalytic activity. The tolerance to fuel cell molecules (e.g., methanol) and the durability of Fe3C@NGC are obviously superior to commercial Pt/C catalysts in alkaline media. The high ORR performance of Fe3C@NGC could be due to its large surface area (313.7 m2 g−1), a synergistic role of Fe3C nanocrystals, N doping in graphitic carbon creating more catalytic active sites, and a porous structure of the nanocomposite facilitating mass transfer to efficiently improve the utilization of these catalytic active sites.
Co-reporter:Xian Zhang, Tianxing Wu, Yunxia Zhang, Dickon H. L. Ng, Huijun Zhao and Guozhong Wang
RSC Advances 2015 vol. 5(Issue 63) pp:51446-51453
Publication Date(Web):21 May 2015
DOI:10.1039/C5RA05184C
Novel hollow mesoporous silica spheres with magnetic cores (HMSMCs) were successfully synthesized by using hybrid magnetic carbon (Fe3O4/C) spheres as templates. The microspheres were further functionalized with (3-mercaptopropyl)trimethoxysilane (MPTS) to produce thiol functionalized HMSMCs (SH-HMSMCs), and their ability to absorb traces of toxic Hg2+ was evaluated. The characterization results revealed that the hollow microspheres were 250–300 nm in diameter. The thickness of the shell was about 50 nm, in which contained an inner core of Fe3O4 crystallites with a size of about 10 nm. It was also found that the saturation magnetization of the sample was 62.5 emu g−1 and the BET surface area was 421 m2 g−1. These magnetic hybrid silica microspheres with thiol functional groups were found to have a high affinity to Hg2+, and were able to reduce even a low concentration of Hg2+ (<1 mg L−1) down to about 0.53 μg L−1, which was less than the Hg2+ content in the drinking water standard. The super strong affinity towards Hg2+ was attributed to the synergistic effect of the thiol groups and the unique structure of the microspheres. Moreover, the microspheres as adsorbents could be easily separated by an external magnetic field, and the adsorbed Hg2+ on the adsorbents could be removed by using hydrochloric acid, thus the adsorbents are readily reusable.
Co-reporter:Yong Yang, Guozhong Wang, Gang Gu, Qian Li, Shenghong Kang, Yunxia Zhang, Dickon H. L. Ng and Huijun Zhao
RSC Advances 2015 vol. 5(Issue 15) pp:11349-11357
Publication Date(Web):05 Jan 2015
DOI:10.1039/C4RA14675A
A facile and economical one-pot microwave-assisted approach for the synthesis of Ag decorated yolk@shell structured TiO2 microspheres (Ag-TS) is reported. The rapid and uniform microwave heating could reduce the reaction time to 30 min, an order of magnitude shorter than that of conventional methods. The characterization data confirmed that the resultant mesoporous structured Ag-TS were highly uniform in size with an average diameter of ∼0.5 μm, which was constructed by small anatase TiO2 nanoparticles, along with Ag nanoparticles ranging from 10 to 50 nm homogeneously dispersed on the microspheres. Nitrogen adsorption–desorption measurement revealed that all the Ag-TS samples had high specific surface areas (>100 m2 g−1) and abundant mesoporous structures. The growth model of Ag-TS was proposed based on a series of contrast experiments, the unique selective heating of reaction solvent (deionized water and ethanol) by the microwave method was found to be critical. At the initial stage, amorphous solid microspheres were formed by heating of ethanol molecules through absorbing microwave energy due to the better microwave absorbing performance. Then water molecules were heated by the microwave irradiation, the crystallization of anatase TiO2 on the surface of the solid microspheres started, followed by the Ti species diffusing spontaneously towards the outer surface of the solid microspheres and leading to the formation of the outer shell due to the Ostwald ripening process. Finally, water continuously diffused through the outer shell and guided the subsequent crystallization of anatase TiO2, resulting in the formation of the core. Besides, the application of Ag-TS for the removal of water contaminants including toxic heavy metal hexavalent chromium (Cr(VI)) ions and organic dye methylene blue (MB) were also evaluated.
Co-reporter:Quan Deng, Haibin Tang, Gang Liu, Xiaoping Song, Shenhong Kang, Huimin Wang, Dickon H. L. Ng and Guozhong Wang
New Journal of Chemistry 2015 vol. 39(Issue 10) pp:7781-7785
Publication Date(Web):12 May 2015
DOI:10.1039/C5NJ00343A
Toxic 2,4,4′-trichlorobiphenyl (PCB28) was photocatalytically degraded by the action of Ag nanoparticle decorated nanosheet-assembled ZnO microspheres via a new photocatalytic degradation pathway. The outright degradation into long-chain alkanes via ring-opening reactions was demonstrated by gas chromatography-mass spectrometry.
Co-reporter:Quan Deng, Haibin Tang, Gang Liu, Xiaoping Song, Guoping Xu, Qian Li, Dickon H.L. Ng, Guozhong Wang
Applied Surface Science 2015 Volume 331() pp:50-57
Publication Date(Web):15 March 2015
DOI:10.1016/j.apsusc.2014.12.202
Highlights
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ZnO nanosheets-assembled microspheres (ZnOs) were prepared.
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Ag nanoparticles (Ag-NPs) were decorated onto the whole surface of the ZnOs.
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The Ag-NPs/ZnOs composite showed enhanced photocatalytic performance to MB and MO.
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Cyclic voltammetry and impedance spectra revealed enhanced charge transportation.
Co-reporter:Yong Yang, Guozhong Wang, Quan Deng, Dickon H. L. Ng, and Huijun Zhao
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 4) pp:3008
Publication Date(Web):January 15, 2014
DOI:10.1021/am405607h
High yield production of micro/nanostructured nanoparticulate TiO2 microspheres (NTMs) via a facile microwave-assisted hydrothermal approach was investigated. The rapid and uniform microwave heating could reduce the reaction time to 30 min, an order of magnitude shorter than that of conventional hydrothermal methods. The characterization data confirmed that the resultant NTMs were highly uniform in size, having an average diameter of ∼0.5 μm. The obtained NTMs were found to be constructed by well-crystallized anatase phase nanoparticles ranging from 5 to 10 nm that can be readily controlled by the microwave radiation temperature. Nitrogen sorption isotherm analysis revealed that the obtained NTMs possessed abundant mesoporous structures with a high specific surface area of 124 m2 g–1. An in situ self-aggregation formation process under controllable pH in presence of urea was proposed. The results obtained from the application of NTMs for simultaneous photocatalytic decontamination of Cr(VI) and methyl orange (MO) demonstrated a strong synergistic effect that dramatically enhanced both Cr(VI) reduction and MO oxidation removal efficiencies. This work not only enriched the synthesis methods of the micro/nanostructured TiO2, but also provided a new means to improve the photocatalytic efficiency via structural-induced synergistic effect, applicable to the other catalysis systems.Keywords: Cr(VI); methyl orange; microwave; photocatalytic; synergistic; TiO2;
Co-reporter:Yong Yang, Guozhong Wang, Quan Deng, Shenghong Kang, Dickon H. L. Ng and Huijun Zhao
CrystEngComm 2014 vol. 16(Issue 15) pp:3091-3096
Publication Date(Web):27 Jan 2014
DOI:10.1039/C3CE42505C
High-energy {100} faceted single crystal TiO2 nanorods were synthesized by a facile hydrothermal method. An interesting phase transition from the orthorhombic hydrogen titanate to anatase TiO2 was observed during the reaction process. A structural formation model of the TiO2 nanorods was proposed based on experimental evidence. The resultant {100} faceted TiO2 nanorods exhibited considerably enhanced photocatalytic activity towards degradation of organic pollutants and removal of heavy metal ions owing to the special one-dimensional structure with the reactive {100} facets, thus showing a great potential in the field of water treatment. At the same time, the synthetic route provided guidance for the synthesis of high-energy {100} facets using EDTA and urea as effective modifiers. This approach may be extended to synthesize other functional oxide crystals with well-defined morphologies and to increase the percentages of certain exposed facets.
Co-reporter:Yong Yang, Guozhong Wang, Quan Deng, Huiming Wang, Yunxia Zhang, Dickon H. L. Ng and Huijun Zhao
RSC Advances 2014 vol. 4(Issue 65) pp:34577-34583
Publication Date(Web):23 Jul 2014
DOI:10.1039/C4RA04787G
Hierarchical structure TiO2 hollow spheres composed of nanometer-sized building blocks, nanoflakes with exposed anatase (001) facets, have been synthesized with a high yield through a facile fluoride-mediated hydrothermal route. The average diameter of the resultant TiO2 hollow spheres is ∼1 μm, and the width of well-crystallized anatase phase nanoflakes is ∼50 nm. Nitrogen adsorption–desorption measurement revealed that the products have a high specific surface area of 26 m2 g−1 and abundant mesoporous structure. The TiO2 hollow spheres were used to photocatalytically degrade Cr(VI) in solution. The results indicate an enhanced photocatalytic activity compared to other TiO2 structures, owing to the high specific surface area and abundant mesoporous properties of the TiO2 hollow spheres. Besides, the presence of the reactive (001) facets also contributed to the enhanced activity; it was found that the (001) facets are more effective in the adsorption of Cr(VI) than the commonly exposed (101) facets. Furthermore, the surface fluorination of TiO2 hollow spheres was found to have a negative role in the photocatalytic removal of Cr(VI). The TiO2 hollow spheres not only can remove Cr(VI) from wastewater; they also can reduce the adsorbed toxic Cr(VI) to Cr(III), further forming oxides or hydroxides. In addition, the TiO2 hollow sphere photocatalysts with micron-scale size showed high durability in the cyclic tests.
Co-reporter:Gang Liu, Quan Deng, Hongqiang Wang, Dickon H. L. Ng, Mingguang Kong, Weiping Cai and Guozhong Wang
Journal of Materials Chemistry A 2012 vol. 22(Issue 19) pp:9704-9713
Publication Date(Web):10 Apr 2012
DOI:10.1039/C2JM31586F
Micro/nanostructured α-Fe2O3 spheres (MNFSs) were fabricated via a surfactant- and template-free method, involving the hydrothermal synthesis of FeCO3 precursor firstly and a subsequent thermal decomposition treatment. The product was characterized by X-ray diffraction, field emission scanning electron microscopy and transmission electron microscopy. The MNFSs had an average diameter of about 5 μm, and each contained subunits of interlinked and elongated particles with size less than 30 nm. The UV-Vis spectrum of MNFSs exhibited visible-light absorption. The visible-light photocatalytic activity of MNFSs was evaluated by using them to degrade the rhodamine 6G pollutant in water at ambient temperature under different parameters such as pH value, the amount of MNFSs and H2O2. We also found that the visible-light photocatalytic activity of MNFSs was higher than that of the micron- and nano-sized α-Fe2O3 particles. The reaction rate of MNFSs was more than twice that of nano-sized α-Fe2O3 and nearly 12 times faster than that of the micron-sized α-Fe2O3. This high photocatalytic feature of MNFSs was attributed to the high specific surface area together with their special porous structure. Importantly, these characteristics could control the rate of releasing ·OH and thus improve the utilization efficiency of ·OH. MNFSs can be easily recycled from the treated water using a magnet due to its magnetic behavior. There was no obvious decrease of the photocatalytic activity of MNFSs after being used.
Co-reporter:Quan Deng, Xiaowei Duan, Dickon H. L. Ng, Haibin Tang, Yong Yang, Mingguang Kong, Zhikun Wu, Weiping Cai, and Guozhong Wang
ACS Applied Materials & Interfaces 2012 Volume 4(Issue 11) pp:6030
Publication Date(Web):October 23, 2012
DOI:10.1021/am301682g
Nanostructured Ag nanoparticles (Ag-NPs)/nanoporous ZnO micrometer-rods (n-ZnO MRs) have been synthesized by a two-step method. The n-ZnO MRs was initially prepared by solvothermal-assisted heat treatment. The rods had the diameter ranged from 90 to 150 nm and length between 0.5 and 3 μm. They were found to be porous and were composited of ZnO nanopartiles with size of about 20 nm. In the second stage, Ag-NPs with a diameter of 20–50 nm were anchored onto the surface of the as-prepared n-ZnO MRs by a photoreduction method. The Ag-NPs/n-ZnO MRs were evaluated for their ability to degrade methylene blue (MB) solution under visible to ultraviolet (UV) light irradiation. The rate of degradation of the as-prepared Ag-NPs/n-ZnO MRs was more than twice and nearly 5.6 times faster than that of using bare n-ZnO MRs under the UV and solar light irradiation, respectively. The formation of Schottky barriers in the regions between the Ag-NPs and n-ZnO MRs had improved the charge separation and consequently enhanced the efficiency of the degradation process. Moreover, the as-prepared hybrid structure exhibited high photostability, and 98% of degradation efficiency could be maintained even after being used five times. This endurance was attributed to the retardation of photocorrosion of ZnO as a result of the low concentration of surface defects in the as-prepared n-ZnO MRs. It also minimized the surface defects of the as-prepared n-ZnO MRs and consequently further inhibited the photocorrosion of ZnO when the deposited Ag-NPs were much more inclined to combine with the chemisorbed oxygen.Keywords: Ag nanoparticles; photocatalytic activities; photoreduction; solvothermal method; ZnO micrometer-rods;
Co-reporter:Dr. Gang Liu;Quan Deng;Huimin Wang;Shenghong Kang;Yong Yang; Dickon H. L. Ng; Weiping Cai; Guozhong Wang
Chemistry - A European Journal 2012 Volume 18( Issue 42) pp:13418-13426
Publication Date(Web):
DOI:10.1002/chem.201200864
Abstract
We present a simple and effective method for the synthesis of nanostructured Fe3O4 micron-spheres (NFMSs) by annealing hydrothermally formed FeCO3 spheres in argon. The phase structure, particle size, and magnetic properties of the product have been characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and by means of a superconducting quantum interference device (SQUID). The results have shown that the as-obtained NFMSs have a diameter of about 5 μm and are composed of nanometer-sized porous lamellae. The NFMSs have a large specific surface area (135.9 m2 g−1), reductive Fe2+ incorporated into their structure, and intense magnetic properties. These properties suggest that NFMSs have potential application in removing toxic Cr6+ ions from polluted water. At 25 °C, each gram of NFMSs product can remove 43.48 mg of Cr6+ ions, as compared to just 10.2 mg for nanometer-sized Fe3O4 and 1.89 mg for micron-sized Fe3O4. The enhanced removal performance can be ascribed to the structural features. Moreover, the Cr6+ ion removal capacity of the NFMSs can reach up to 71.2 mg g−1 at 50 °C. The influencing parameters in the removal of Cr6+ ions, such as contact time, pH, and temperature, have been evaluated. The Cr6+-removal mechanism has been investigated. We have found that the NFMSs product not only serves as an effective adsorbent to remove toxic Cr6+ ions from polluted water, but also as an effective reductant in reducing the adsorbed toxic Cr6+ ions to much less toxic Cr3+ through the Fe2+ incorporated into its structure.
Co-reporter:Xiaowei Duan, Guozhong Wang, Hongqiang Wang, Yongqiang Wang, Chen Shen and Weiping Cai
CrystEngComm 2010 vol. 12(Issue 10) pp:2821-2825
Publication Date(Web):20 Apr 2010
DOI:10.1039/B922679F
Rod-like ZnO micro-nanostructures have been synthesized by a solvothermal-assisted heat treatment method. The micro-nanostructures consist of polycrystalline nanoparticles with a hexagonal wurtzite structure. The diameter and length of the nanorods are about 90–150 nm and 0.6–3 μm, respectively. Nitrogen sorption isotherm analysis reveals a bi-pore-size-distribution feature of ZnO micro-nanostructures and the origin of this peculiar pore-size distribution may be ascribed to the polar feature of ZnO crystals. Importantly, these micro-nanostructures have superior photocatalytic activity and high durability in the degradation of organic dyes.
Co-reporter:Yongqiang Wang Dr., ;Hongqiang Wang Dr.;Changhao Liang;Weiping Cai ;Lide Zhang
Chemistry - A European Journal 2010 Volume 16( Issue 11) pp:3497-3503
Publication Date(Web):
DOI:10.1002/chem.200902799
Abstract
Micro/nanoscale magnesium silicate hollow spheres were synthesized by using silica colloidal spheres as a chemical template in one pot. The hollow spherical structure, consisting of well-separated nanoscale units, was microscale as a whole and could be easily handled in solution. The as-synthesized magnesium silicate hollow spheres with large specific surface area showed availability for the removal of organic and heavy-metal ions efficiently from waste water. Importantly, the micro/nanoscale magnesium silicate hollow spheres that had adsorbed organic pollutants could be regenerated by calcination and used repeatedly in pollutant removal. Magnesium silicate hollow spheres synthesized by a scaled-up chemical template method may have potential applications in removing cationic dyes and heavy-metal ions from waste water.
Co-reporter:Yongqiang Wang, Chunjuan Tang, Quan Deng, Changhao Liang, Dickon H. L. Ng, Fung-luen Kwong, Hongqiang Wang, Weiping Cai, Lide Zhang, and Guozhong Wang
Langmuir 2010 Volume 26(Issue 18) pp:14830-14834
Publication Date(Web):August 19, 2010
DOI:10.1021/la101805v
A versatile method was developed to synthesize nickel silicate, silica, and silica−nickel composite porous hollow spheres by using silica spheres as templates. In the preparation, silica spheres were treated with a mixture of NiSO4·6H2O and NH3·H2O. The nickel-based ingredient reacted with the silica to form a shell while the alkaline solution could remove the silica core, thus forming the nickel silicate hollow spheres. After these spheres were further treated with hydrogen in reduction or with HCl in etching, they became silica−nickel hollow spheres or silica hollow spheres, respectively. The sizes of these hollow spheres depended on the concentration of the precursor. Our investigation also found that their surface properties or magnetic properties could be tailored by adjusting the fabrication parameters.
Co-reporter:Jie Li, Guozhong Wang, Hongqiang Wang, Chunjuan Tang, Yongqiang Wang, Changhao Liang, Weiping Cai and Lide Zhang
Journal of Materials Chemistry A 2009 vol. 19(Issue 15) pp:2253-2258
Publication Date(Web):23 Feb 2009
DOI:10.1039/B816823G
A novel hierarchical Bi0.5Na0.5TiO3 (BNT) micro/nanostructure was synthesized viain situself-assembly of BNT nanocrystals under hydrothermal conditions. Each spheric flower-like BNT micro/nanostructure is composed of nanosheetsca. 100 nm in width, 300 nm in length and 10 nm in thickness. The self-assembly growth process of hierarchical BNT micro/nanostructures from BNT nanocrystals was investigated by changing the reaction time, the molar ratio of precursors and NaOH concentration. From time-dependent morphology evolution, a two-step growth mechanism was proposed to explain the growth of the hierarchical BNT micro/nanostructure. Importantly, such structured BNT shows better photocatalytic performance in the photodegradation of methyl orange than that of the powders of spheric and cubic structured BNT. The intrinsic structure of BNT may contribute to its higher surface-to-volume ratio and stability against overdue aggregation. This study not only gives insights into the hierarchical growth behavior of BNT complex micro/nanoarchitectures, but also provides an efficient route for enhancing the photocatalytic performance of BNT.
Co-reporter:Yongqiang Wang, Guozhong Wang, Hongqiang Wang, Weiping Cai and Lide Zhang
Chemical Communications 2008 (Issue 48) pp:6555-6557
Publication Date(Web):11 Nov 2008
DOI:10.1039/B816751F
A new type of hierarchical structure, copper silicate hollow spheres assembled by nanotubes, was synthesized via a simple one-pot route by using silica colloidal spheres as chemical template.
Co-reporter:Zhengfu Zhao, Xian Zhang, Hongjian Zhou, Gang Liu, Mingguang Kong, Guozhong Wang
Microporous and Mesoporous Materials (April 2017) Volume 242() pp:
Publication Date(Web):April 2017
DOI:10.1016/j.micromeso.2017.01.006
•Monodispersed FMMS composites were synthesized via the microwave-assisted hydrothermal method.•The FMMS composites have magnetic property and high affinity toward metal ions.•The FMMS composites have the good selectivity for the Cu2, Pb2+ and Cd2+ ions.•The mesoporous structures of the FMMS composites increased the amount of surface active adsorption sites.•The FMMS composites exhibited excellent sorption-regeneration performance.An ultrafast and facile microwave assisted hydrothermal approach was applied to synthesize magnetic Fe3O4-mesoporous magnesium silicate (FMMS) core-shell composites for effective removal of Cu2+, Cd2+ and Pb2+ from aqueous solutions. The FMMS composites have mesoporous magnesium silicate shells encapsulated Fe3O4 spheres core structures, and the mesoporous shell assembled by a large number of intercrossed nanosheets with a diameter of 4.0 nm pores, thus exhibited the excellent capability to remove Pb2+ (223.2 mg/g) and Cu2+ (53.5 mg/g) ions from aqueous solutions. The superior removal capacity of the FMMS composites can be ascribed to its mesoporous structures with abundant adsorption active sites. The competitive adsorption studies showed that the adsorbent affinity order of three metal ions by FMMS composites is Cu2+>Pb2+>Cd2+. It is noteworthy that the heavy metal ions could not only adsorb on the surface of FMMS composites, but also intercalate into the intercrossed nanosheets of mesoporous magnesium silicate shell, which reveals the synergistic effect of the electrostatic attraction, surface complexation and ion exchange coupled with the adsorption bonding with surface hydroxyl groups. Furthermore, the FMMS composites exhibited excellent sorption-regeneration performance, which can be easily separated and recovered by external magnet. All results demonstrated that the magnetic FMMS core-shell composite was a promising sorbent material for the preconcentration and separation of heavy metal ions from the waste water.
Co-reporter:Xinxin Ye, Shenghong Kang, Huimin Wang, Hongying Li, Yunxia Zhang, Guozhong Wang, Huijun Zhao
Journal of Hazardous Materials (30 May 2015) Volume 289() pp:210-218
Publication Date(Web):30 May 2015
DOI:10.1016/j.jhazmat.2015.02.052
•We modify natural diatomite using the facile acid treatment and ultrasonication.•Modification add pore volume, surface area and electronegativity of natural diatomite.•Modified diatomite is superior to natural diatomite in soil heavy metal remediation.•Modified diatomite can be promising for in-situ immobilization of heavy metal in soil.Natural diatomite was modified through facile acid treatment and ultrasonication, which increased its electronegativity, and the pore volume and surface area achieved to 0.211 cm3 g−1 and 76.9 m2 g−1, respectively. Modified diatomite was investigated to immobilize the potential toxic elements (PTEs) of Pb, Cu and Cd in simulated contaminated soil comparing to natural diatomite. When incubated with contaminated soils at rates of 2.5% and 5.0% by weight for 90 days, modified diatomite was more effective in immobilizing Pb, Cu and Cd than natural diatomite. After treated with 5.0% modified diatomite for 90 days, the contaminated soils showed 69.7%, 49.7% and 23.7% reductions in Pb, Cu and Cd concentrations after 0.01 M CaCl2 extraction, respectively. The concentrations of Pb, Cu and Cd were reduced by 66.7%, 47.2% and 33.1% in the leaching procedure, respectively. The surface complexation played an important role in the immobilization of PTEs in soils. The decreased extractable metal content of soil was accompanied by improved microbial activity which significantly increased (P < 0.05) in 5.0% modified diatomite-amended soils. These results suggested that modified diatomite with micro/nanostructured characteristics increased the immobilization of PTEs in contaminated soil and had great potential as green and low-cost amendments.
Co-reporter:Yanping Su, Chun Chen, Xiaoguang Zhu, Yong Zhang, Wanbing Gong, Haimin Zhang, Huijun Zhao and Guozhong Wang
Dalton Transactions 2017 - vol. 46(Issue 19) pp:NaN6365-6365
Publication Date(Web):2017/04/10
DOI:10.1039/C7DT00628D
We report a fast and simple method for the synthesis of Ni-based metal–organic-frameworks (Ni-MOFs). Due to the existence of nickel ions and an organic ligand, the MOFs are employed as a sacrificial template for the facile preparation of carbon-embedded Ni (Ni/C) catalysts by a direct thermal decomposition method. The obtained Ni/C catalysts exhibit excellent catalytic activity for selectively transforming furfural (FAL) to tetrahydrofurfuryl alcohol (THFOL) due to the Ni nanoparticles (NPs) embedded uniformly in the ligand-derived carbon. The exemplified results illustrate that the catalytic performance of the Ni/C catalyst is greatly affected by the calcination conditions (temperature and time), composition of the Ni-MOF precursor and the catalysis conditions. The conversion of FAL and selectivity of THFOL both reached 100% under the conditions of 120 °C, 1 MPa H2 pressure and 120 min of hydrogenation over the Ni/C-500 catalyst, derived from the pyrolysis of Ni-MOFs (Ni:BTC mole ratio of 1.0) at 500 °C for 120 min, which exhibits an average nanoparticle size of ∼14 nm and uniform dispersion, and the highest BET surface area (∼92 m2 g−1) among all investigated Ni/C catalysts. This facilely prepared heterogeneous catalyst would be very promising for the replacement of noble metal catalysts for the efficient catalytic conversion of biomass-derived feedstocks into value-added chemicals.
Co-reporter:T. X. Wu, G. Z. Wang, X. Zhang, C. Chen, Y. X. Zhang and H. J. Zhao
Chemical Communications 2015 - vol. 51(Issue 7) pp:NaN1337-1337
Publication Date(Web):2014/11/27
DOI:10.1039/C4CC09355K
Chitosan, the only alkaline polysaccharide in nature with rich nitrogen content, is used as the sole precursor to obtain N-doped graphitic carbon-based ORR electrocatalysts. The findings of this work demonstrate that cheap, plentiful and renewable biomasses can be transformed into high value functional carbon materials.
Co-reporter:Yongqiang Wang, Guozhong Wang, Hongqiang Wang, Weiping Cai and Lide Zhang
Chemical Communications 2008(Issue 48) pp:NaN6557-6557
Publication Date(Web):2008/11/11
DOI:10.1039/B816751F
A new type of hierarchical structure, copper silicate hollow spheres assembled by nanotubes, was synthesized via a simple one-pot route by using silica colloidal spheres as chemical template.
Co-reporter:Zhigang Geng, Haimin Zhang, Qizhong Xiong, Yunxia Zhang, Huijun Zhao and Guozhong Wang
Journal of Materials Chemistry A 2015 - vol. 3(Issue 38) pp:NaN19460-19460
Publication Date(Web):2015/08/20
DOI:10.1039/C5TA05610A
In this work, a three-dimensional (3D) chitosan hydrogel with superior fluorescence properties was successfully fabricated by modifying chitosan fibers with glutaric dialdehyde (GD) via a simple cross-linking approach. The resulting three-dimensional fluorescent chitosan hydrogel (3D-FCH) with hydrophilic properties exhibited a strong blue fluorescence emission at an excitation wavelength of 337 nm. The fluorescence mechanism of the as-synthesized 3D-FCH was investigated and proposed in detail using X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR) techniques. As a solid-phase fluorescent probe, the 3D-FCH was used to selectively and sensitively determine mercury(II) (Hg2+) ions in aqueous media. The results demonstrated that a prominent fluorescence quenching at 401 nm was observed in the presence of Hg2+ with a linear response range of 5.0–50 nM and an estimated limit of detection of 0.9 nM. The fluorescence quenching mechanism could be ascribed to the strong complexation between Hg2+ and the GD fluorophore with a conjugate structure. Moreover, the porous structure of the chitosan hydrogel and the high adsorption capacity of the chitosan fibers in the hydrogel could be very favorable for the rapid fluorescence determination of Hg2+. This work may pave a new way to develop low-cost fluorescent chitosan hydrogels as solid-phase fluorescence determination platforms to replace traditional liquid-phase fluorophores for application in the fluorescence detection of heavy metal ions.
Co-reporter:Tianxing Wu, Haimin Zhang, Xian Zhang, Yunxia Zhang, Huijun Zhao and Guozhong Wang
Physical Chemistry Chemical Physics 2015 - vol. 17(Issue 41) pp:NaN27533-27533
Publication Date(Web):2015/09/15
DOI:10.1039/C5CP04252F
In this work, chitosan whiskers (CWs) were first extracted using low-cost and earth-abundant crab shells as materials by a series of chemical processes, and then assembled into chitosan whisker microspheres (CWMs) via a simple photochemical polymerization approach. Subsequently, a cementite (Fe3C) nanocrystal@N-doped graphitic carbon (Fe3C@NGC) nanocomposite was successfully fabricated by high temperature pyrolysis of CWMs adsorbed with ferric acetylacetonate (Fe(acac)3) at 900 °C. It was found that a suitable growth atmosphere generated inside CWMs during high temperature pyrolysis is critically important to form Fe3C nanocrystal cores, concurrently accompanying a structural transformation from chitosan whiskers to mesoporous graphitic carbon shells with natural nitrogen (N) doping properties, resulting in the formation of a core–shell structure Fe3C@NGC nanocomposite. The resulting samples were evaluated as electrocatalysts for oxygen reduction reaction (ORR). In comparison with sole N-doped graphitic carbon without Fe3C nanocrystals obtained by direct pyrolysis of chitosan whisker microspheres at 900 °C (CWMs-900), Fe3C@NGC showed significantly improved ORR catalytic activity. The tolerance to fuel cell molecules (e.g., methanol) and the durability of Fe3C@NGC are obviously superior to commercial Pt/C catalysts in alkaline media. The high ORR performance of Fe3C@NGC could be due to its large surface area (313.7 m2 g−1), a synergistic role of Fe3C nanocrystals, N doping in graphitic carbon creating more catalytic active sites, and a porous structure of the nanocomposite facilitating mass transfer to efficiently improve the utilization of these catalytic active sites.
Co-reporter:Rongrong Liu, Haimin Zhang, Shengwen Liu, Xian Zhang, Tianxing Wu, Xiao Ge, Yipeng Zang, Huijun Zhao and Guozhong Wang
Physical Chemistry Chemical Physics 2016 - vol. 18(Issue 5) pp:NaN4101-4101
Publication Date(Web):2016/01/07
DOI:10.1039/C5CP06970J
Development of cheap, abundant and metal-free N-doped carbon materials as high efficiency oxygen reduction electrocatalysts is crucial for their practical applications in future fuel cell devices. Here, three-dimensional (3D) N-doped porous carbon (NPC) materials have been successfully developed by a simple template-assisted (e.g., SiO2 spheres) high temperature pyrolysis approach using shrimp-shell derived N-doped carbon nanodots (N-CNs) as carbon and nitrogen sources obtained through a facile hydrothermal method. The shrimp-shell derived N-CNs with a product yield of ∼5% possess rich surface O- and N-containing functional groups and small nanodot sizes of 1.5–5.0 nm, which are mixed with surface acidification treated SiO2 spheres with an average diameter of ∼200 nm in aqueous solution to form a N-CNs@SiO2 composite subjected to a thermal evaporation treatment. The resultant N-CNs@SiO2 composite is further thermally treated in a N2 atmosphere at different pyrolysis temperatures, followed by acid etching, to obtain 3D N-doped porous carbon (NPC) materials. As electrocatalysts for oxygen reduction reaction (ORR) in alkaline media, the experimental results demonstrate that 3D NPC obtained at 800 °C (NPC-800) with a surface area of 360.2 m2 g−1 exhibits the best ORR catalytic activity with an onset potential of −0.06 V, a half wave potential of −0.21 V and a large limiting current density of 5.3 mA cm−2 (at −0.4 V, vs. Ag/AgCl) among all NPC materials investigated, comparable to that of the commercial Pt/C catalyst with an onset potential of −0.03 V, a half wave potential of −0.17 V and a limiting current density of 5.5 mA cm−2 at −0.4 V. Such a 3D porous carbon ORR electrocatalyst also displays superior durability and high methanol tolerance in alkaline media, apparently better than the commercial Pt/C catalyst. The findings of this work would be valuable for the development of low-cost and abundant N-doped carbon materials from biomass as high performance metal-free electrocatalysts.
Co-reporter:Jie Li, Guozhong Wang, Hongqiang Wang, Chunjuan Tang, Yongqiang Wang, Changhao Liang, Weiping Cai and Lide Zhang
Journal of Materials Chemistry A 2009 - vol. 19(Issue 15) pp:NaN2258-2258
Publication Date(Web):2009/02/23
DOI:10.1039/B816823G
A novel hierarchical Bi0.5Na0.5TiO3 (BNT) micro/nanostructure was synthesized viain situself-assembly of BNT nanocrystals under hydrothermal conditions. Each spheric flower-like BNT micro/nanostructure is composed of nanosheetsca. 100 nm in width, 300 nm in length and 10 nm in thickness. The self-assembly growth process of hierarchical BNT micro/nanostructures from BNT nanocrystals was investigated by changing the reaction time, the molar ratio of precursors and NaOH concentration. From time-dependent morphology evolution, a two-step growth mechanism was proposed to explain the growth of the hierarchical BNT micro/nanostructure. Importantly, such structured BNT shows better photocatalytic performance in the photodegradation of methyl orange than that of the powders of spheric and cubic structured BNT. The intrinsic structure of BNT may contribute to its higher surface-to-volume ratio and stability against overdue aggregation. This study not only gives insights into the hierarchical growth behavior of BNT complex micro/nanoarchitectures, but also provides an efficient route for enhancing the photocatalytic performance of BNT.
Co-reporter:Gang Liu, Quan Deng, Hongqiang Wang, Dickon H. L. Ng, Mingguang Kong, Weiping Cai and Guozhong Wang
Journal of Materials Chemistry A 2012 - vol. 22(Issue 19) pp:NaN9713-9713
Publication Date(Web):2012/04/10
DOI:10.1039/C2JM31586F
Micro/nanostructured α-Fe2O3 spheres (MNFSs) were fabricated via a surfactant- and template-free method, involving the hydrothermal synthesis of FeCO3 precursor firstly and a subsequent thermal decomposition treatment. The product was characterized by X-ray diffraction, field emission scanning electron microscopy and transmission electron microscopy. The MNFSs had an average diameter of about 5 μm, and each contained subunits of interlinked and elongated particles with size less than 30 nm. The UV-Vis spectrum of MNFSs exhibited visible-light absorption. The visible-light photocatalytic activity of MNFSs was evaluated by using them to degrade the rhodamine 6G pollutant in water at ambient temperature under different parameters such as pH value, the amount of MNFSs and H2O2. We also found that the visible-light photocatalytic activity of MNFSs was higher than that of the micron- and nano-sized α-Fe2O3 particles. The reaction rate of MNFSs was more than twice that of nano-sized α-Fe2O3 and nearly 12 times faster than that of the micron-sized α-Fe2O3. This high photocatalytic feature of MNFSs was attributed to the high specific surface area together with their special porous structure. Importantly, these characteristics could control the rate of releasing ·OH and thus improve the utilization efficiency of ·OH. MNFSs can be easily recycled from the treated water using a magnet due to its magnetic behavior. There was no obvious decrease of the photocatalytic activity of MNFSs after being used.
