•The interaction of nickel clusters with doped graphene were studied using DFT.•Pyridinic N/B doped defective graphene improved the interactions with Nin clusters.•There was enhanced hybridization of Ni-C on PBG, evidenced by PDOS analysis.•B and N doped graphene are potential supports to stabilize the metal cluster.The doping effects of nitrogen or boron atom on the stability of defective graphene supported Nin (n = 1–6) clusters were explored using density functional theory (DFT) approaches, while the configurations of pyridinic-B and pyridinic-N doped defective graphene (PBG, PNG) were constructed. The binding energies of Nin clusters on doped defective graphene are both higher than that of Nin on pristine graphene (PG). It is indicated that the interaction between Nin clusters and doped graphene is enhanced. PBG has a stronger interaction with Nin clusters than PNG, and shows a more favorable ability to stabilize Nin clusters. Further, both PBG and PNG carriers provide sufficient positions for binding Ni atoms. The binding site for Ni1 and Ni2 cluster on PBG shifts from the vacancy site to the five-membered ring for Ni3 - Ni6 clusters. For the PNG, the defects are the anchoring sites for depositing Nin clusters. According to the Hirshfeld charge analysis, the Nin-PBG system shows a different charge transfer way from Nin-PNG.Schematic drawings of Ni4 cluster supported on pristine graphene and pyridinic B- or N-doped graphene were supposed.The adsorption energy indicated that pyridinic B- or N-doped can promote the interaction between Ni4 cluster and graphene substrates.Download high-res image (174KB)Download full-size image

A series of Pd/TiO2 catalysts were prepared by incipient wetness impregnation method followed by atmospheric discharge plasma treatment. In order to study the influences of plasma treatment on the catalysts, the samples were characterized by XRD, TPR, TPD, XPS and TEM technologies. It was found that the plasma treatment catalysts possessed a higher acetylene conversion and ethylene selectivity compared to those of the untreated sample. The enhanced performance of the plasma treated catalyst was mainly dependent on two main effects. On one hand, the treated catalyst possessed a higher metal Pd dispersion, which resulted in the easier activation of acetylene. On the other hand, the surface electron density of metal Pd on the treated catalyst got enhanced compared to that of untreated sample, because of the stronger interaction between TiO2 support and metallic Pd, helping the more desorption of ethylene species from the surface of catalyst.

AbstractZnO-Al2O3 derived from layered double hydroxides (ZnAl-LDH) was successfully applied for dispersion of Pd-Ag bimetallic catalysts for the selective hydrogenation of acetylene to ethylene and the Pd-Ag/ZnO-Al2O3 catalyst showed the best catalytic performance among the prepared samples. It was found that the catalyst carrier of ZnO-Al2O3 metal-oxides derived form ZnAl-LDH could significantly suppress the over-hydrogenation of acetylene to obtain the relatively higher selectivity of ethylene. The introduction of Ag restricted efficiently the formation of coke because of the oligomerization reaction, which was further evidenced by thermal gravimetric analysis. The selectivity towards ethylene was in the order of Pd-Ag/ZnO-Al2O3>Pd/ZnO-Al2O3>Pd-Ag/Al2O3>Pd/Al2O3 at a high conversion level. As the thermal gravimetric and differential temperature analysis (TG-DTA) revealed, Pd-Ag intermetallic catalyst on the ZnO-Al2O3 support showed less coke formation.

•α-Phase NiCo double hydroxide (NiCo DH) was successfully synthesized via a rapid microwave heating method.•The as-synthesized NiCo DH presented a 3D flower-like microsphere superstructure composed of ultrathin nanosheets.•NiCo DH showed a long term stability at high current density.•The asymmetric supercapacitor delivered a high energy density and good stability.Fast and low-cost fabrication of high performance electrode materials is of great importance for the application of supercapacitors. Herein, in our research, three-dimensional (3D) flower-like NiCo double hydroxide (NiCo DH) microsphere was successfully synthesized via a rapid, inexpensive and energy-saving microwave route without using any template or surfactant under atmospheric pressure. The as-obtained NiCo DH microsphere endowed with α-phase structure with CNO− ions intercalation in the interlayers (7.3 Å) was composed of ultrathin nanosheets with thickness less than 10 nm. Electrochemical test revealed the NiCo DH electrode showed a high specific capacitance of 1120 F g−1 at 1 A g−1 and remained 996 F g−1 at 10 A g−1 (88.9% retention). Moreover, after 2000 cycles, the capacitance reached 122.5% of its initial value at 10 A g−1 and still retained 93.8% at 30 A g−1 after another 1000 cycles, showing superb stability compared with reported α-phase hydroxides. The admirable stability could be attributed to the synergistic effect between Ni and Co elements, the ion exchange phenomenon between CNO− and OH− ions in the interlayer of NiCo DH during cycling test, and the coherent 3D superstructure. Besides, the asymmetric supercapacitor, with NiCo DH as positive electrode and activated carbon from coal as negative electrode, delivered a superior energy density of 42.5 Wh kg−1. Consequently, the pleasant synthesis procedure and excellent integrated performance of NiCo DH enable it to be a promising electrode material for the energy storage devices.The 3D flower-like α-phase NiCo DH microsphere synthesized by microwave heating displayed excellent stability. The capacitance increased to 1220 F g−1 after 2000 cycles at 10 A g−1 (122.5% of its initial value of 996 F g−1) and still remained a high capacitance of 822 F g−1 (93.8% retention) after another 1000 cycles at 30 A g−1.Download high-res image (113KB)Download full-size image

•Vanadium-based catalysts for selective oxidation of light alkanes were summarized.•Synthesis and characterization methods for active vanadium catalyst were discussed.•Reaction temperature and performance was related to understand vanadium catalyst.Vanadium compounds have attracted much attention because they have widely been used for homogeneous and heterogeneous catalysis field, especially in the selective oxidation of light alkanes, where vanadium-based catalysts were announced to be one of the most efficient catalysts. The present mini-review analyzed the recent developments for the preparation using new synthesis approaches of vanadium based catalysts, and their catalytic performances in the selective oxidation reactions of light alkanes. The influences of several synthesis strategies on the catalytic performances were illustrated in detail, while the samples characterizations were briefly presented.Download high-res image (201KB)Download full-size image

The synergy between ceria and loaded metal nanocrystals (NCs) greatly promotes the catalytic properties for many reactions. Nevertheless, the clear relevance of structures to properties in catalytic systems is hard to establish in that the catalysts studied either featured unstable microstructures or were too heterogeneous. Herein, we show both the facile tool of NC assembly to derive stable and efficient catalytic materials, in which the metal NCs are tailored in terms of their spatial positioning on the nanometer scale (i.e., entrapped in the internal concave ceria surface or deposited on the external convex ceria surface), and how to probe their structure–function relationship. The performance for producing renewable energy sources from hazardous greenhouse gases on a NCs-in-concavities structure is distinct from that on a NCs-on-convexities configuration, elucidating a pivotal impact by the spatial positioning. The current investigation suggests that there exists a clear relationship between the surface adsorbate bonding strength/type and the catalytic properties in reforming CO2/CH4 to hydrogen energy and syngas. Control over the bonding strength/type and activation mechanism of the adsorbates on the catalyst surfaces through changing the support surface curvature orientation is indicated to be a potential strategy for modulating the reaction activity. The insights focus on grasping the surface chemistry of the ceria surface curvature in optimizing the catalysts and can be enlightening for rationally exploring other state-of-the-art heterogeneous nanomaterials.

The morphology and crystal-plane effects of CeO2 materials (nanorods, nanocubes, nanooctas and nanoparticles) on the catalytic performance of Ni/CeO2 in methane dry reforming were investigated. The XRD and Raman results showed that Ni species can be incorporated into the lattices and induce the increase of oxygen vacancies by occupying the vacant sites in the CeO2 nanomaterials. The reaction experiments showed that the catalysts supported over CeO2 nanorods achieved significantly higher catalytic activity and better stability than the other three catalysts. This improved activity was closely related to the strong metal–support interaction between Ni and CeO2 nanorods, which showed great superiority in anchoring Ni nanoparticles. The oxygen vacancies and the mobility of lattice oxygen also showed morphology dependence. They can participate in the catalytic reaction and be favorable for the elimination of carbon deposition. Resistance to carbon deposition was found over the Ni/CeO2-nanorod catalyst, whereas large quantities of graphitic carbon species were formed over the Ni/CeO2-nanocube catalysts, which was responsible for deactivation.

It has been a great challenge to develop an efficient and stable catalyst for dry reforming of methane with carbon dioxide. A new catalyst was synthesized with the catalytically active component in both the lattice and on the surface of the mesoporous support. A remarkable improvement in the catalytic performance of Ni nanocrystals assembled inside pore channels of mesostructured Ni-doped ceria was observed. The initial activity and long-term stability of the sample substantially surpassed that of samples without the intermixed oxide and/or a nonporous architecture, even though the latter was more available. Such an effect concerning a collaborative function stemming from a mesostructure and solid solution has been rarely reported previously in catalysis involving CeO2. We believe that this finding might be of a very generic character and be extended to lots of similar fields. It is expected that the results here can spur experimental and theoretical investigation to promote fundamental comprehension of host–guest or metal–oxide interplay in CeO2-based composite materials.

•High activity and stability catalyst was synthesized by ultrasonic-assisted co-impregnation.•The addition of ceria had great promotion effect on the catalytic performance.•The confinement effect of carbon nanotubes prevented the active phase migration and sintering.Nickel-based catalysts supported on multi-walled carbon nanotubes (CNTs) promoted with cerium were successfully synthesized by ultrasonic-assisted co-impregnation, using γ-Al2O3 as comparative support, and employed in the carbon dioxide methanation reaction. Results indicated that the exceptional properties of CNTs together with the accession of cerium effectively enhanced the dispersion of metallic nickel, promoted the reduction of metal oxides and accelerated the CO2 activation. Meanwhile, the confinement effect of CNTs and the promotion effect of cerium could efficiently prevent the active species migration and sintering, and restricted the carbon deposition reaction. Catalytic performances exhibited that 12Ni4.5Ce/CNT catalyst possessed the highest activity with 83.8% conversion of CO2 and almost 100% selectivity of CH4 without obvious deactivation after 100 h stability test under reaction conditions.CNTs-supported nickel catalyst promoted with cerium was synthesized by ultrasonic-assisted co-impregnation. The optimized catalyst achieved high activity and stability for the carbon dioxide methanation.

Carbon materials have attracted much attention in many applications. Herein, high performance activated carbons (ACs) were synthesized from cheap coal raw material via a facile strategy by KOH activation. AC4T800t2 exhibited the higher BET surface area (2457 m2 g−1) and larger total pore volume (1.448 cm3 g−1) among the as-synthesized ACs samples. The optimized material (AC4T800t2) displayed a specific capacitance as high as 384 F g−1 at a scan rate of 5 mV s−1 in 6 M KOH. The capacitance remained still at 279 F g−1, even at a high scan rate of 200 mV s−1, showing good rate performance. AC4T800t2 also showed excellent cycle performance (95% retention capacity after 5000 cycles) at a current density of 5 A g−1. Furthermore, these ACs samples for CO2 sorption were also investigated using a pressure swing adsorption (PSA) process. The CO2 sorption behaviors of these samples were tested at 298.15 K in a pressure range of 0–1 MPa by the volumetric method. The Langmuir model provided good agreement with the experimental data (correlation coefficient above 0.99). The optimized material (AC4T800t2) showed a high CO2 sorption capacity of 169.44 mL g−1 (7.56 mmol g−1) at 1 MPa, also a high CO2 saturated uptake of 20.81 mmol g−1 (91.56 wt%). Better CO2 uptake is dependent on a larger micropore volume and higher specific surface area. In brief, the high performance AC samples have been synthesized for supercapacitors and CO2 sorption.

•Methane adsorption isotherms over four activated carbons (ACs) were investigated.•Pore size of ACs with unimodal distribution reflected the fractal dimension.•Monolayer adsorbed modal of methane absorption over ACs is evidenced.•Surface area as parameter directly proclaims methane adsorption capacity over ACs.This work was based on methane adsorption over four activated carbons with different micropore structures. Applying the more precise D–A adsorption model, the heterogeneity of activated carbon was proved to be initial factor influencing methane adsorption. The correlation between the microporosity and methane adsorption capacity were discussed in detail. The average pore size of activated carbons with unimodal distributed micropores acted as a reflection of fractal dimension. A linear relationship between surface area and methane adsorption capacity were revealed, indicating monolayer adsorption model of methane on activated carbon. The surface area, as an available microstructure parameter, can be applied as a direct index for estimating the methane adsorption over serious of activated carbons.

•Methods for estimating pseudo-saturation vapor pressure were investigated.•A procedure of determining the parameter, k, in ps = pc(T/Tc)k was proposed.•The influence of the characteristic curve form on the prediction was investigated.•A new form of the characteristic curve was proposed.To acquire the required information of the adsorption system under supercritical conditions, four different rank coals were selected as studied samples. The textures of the coals were characterized through N2 adsorption at 77 K. Their surface morphologies were analyzed by scanning electron microscopy (SEM). The high pressure adsorption data of methane on the coals were obtained at supercritical temperatures. The data were analyzed using the Dubinin–Astakhov (D–A) and Langmuir models. The methods for estimating pseudo-saturation vapor pressure were investigated. And the influence of the characteristic curve form on the D–A equation prediction was investigated. The results show that the constants derived by matching the experimental data to the Langmuir model might lack physical significance, though the Langmuir model was of the correct qualitative form to represent the isotherms of methane on coals. The method for estimating pseudo-saturation vapor pressures proposed by Schwarz failed to render the experimental data to fall onto one characteristic curve. A modified procedure of determining the value of parameter k in Schwarz's equation, i.e. ps = pc(T/Tc)k was proposed. It was found that the modified approach gave the most suitable temperature-independent characteristic curves with determination coefficient R2 > 0.9943. The form of the characteristic curve could influence the D–A model prediction. Using cubic polynomial as characteristic curve form would result in an abnormal prediction i.e. the adsorption amount would increase with the pressure dropping when the pressure is less than approximately 0.9 MPa for Xingq-1–5# and Xujd-1#, 0.8 MPa for Qingh-2–3#, and 0.5 MPa for Leiy-1#. A new form of the characteristic curve deduced from D–A equation was proposed. The prediction uncertainty of D–A equation by using this new characteristic curve form is less than 2.43%.

A simple and novel method, water-assisted chemical vapor deposition (CVD) was developed to functionalize multi-walled carbon nanotubes (MWCNTs) during the synthesis process. The functionalized MWCNTs were characterized using Raman spectroscopy, XPS, TGA, NH3-TPD, SEM and HR-TEM. It was found that new defects are introduced and the amount of acidic groups is increased on the MWCNT surface during the water-assisted CVD process. The amount of C–OH and C–O group on the MWCNT surface is found to be increased from 21.1% to 42% with water vapor assistance. Density functional theory (DFT) was employed to study the chemical behavior of water vapor molecule on the catalyst particle surface of Ni(1 1 1) cluster. Based on the experimental and DFT simulation results, a mechanism for functionalization of MWCNTs by water-assisted CVD is proposed.Graphical abstractWater is adsorbed and activated on Ni surface, then dissociated into OH and O species, followed by part of OH and O species desorbed from the surface. Finally, the desorbed OH and O species oxidize the unsaturated carbon atoms of carbon nanotubes, form defects and oxygen-containing groups.Highlights► MWCNTs were functionalized by water-assisted CVD method. ► Defects and weak-medium acidic sites were created on the MWCNT sidewalls. ► Oxygen-containing groups in functionalized MWCNT were increased from 21.1% to 42%. ► A mechanism for the influence of water vapor on MWCNTs was proposed.

Ruthenium (Ru) was supported on either interior or exterior surface of carbon nanotubes (CNTs) to study the effects of catalytic site positions on the conversion of cellobiose. The catalyst with Ru particles dispersed on the interior CNT surface (Ru-in-CNTs) exhibits higher catalytic activity and better stability than that of Ru particles supported on the exterior surface. It was found that the encapsulation of Ru particles inside the CNT channels improves the reducibility of Ru and decreases the leaching of catalytic sites, which could be the reasons behind the enhanced catalytic performance of Ru-in-CNTs catalyst.

The boron doped titanium oxide hybrid hollow microspheres were easily prepared by hydrothermal method. The scanning and transmission electron microscopy images demonstrated that the hybrid hollow microspheres possessed smooth outer shell and hollow interior. Their crystal structure, chemical state, amount of surface active groups and spectral response region were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, infrared spectra and UV–Vis diffuse reflection spectra, respectively. Methylene blue aqueous solution served as a target pollutant to evaluate the photo-catalytic activity under simulated sunlight. It turned out a higher photo-catalytic activity of boron doped hybrid hollow microspheres, comparing with the undoped ones.Research highlights▶ Facile route successfully fabricated B-doped hybrid hollow microspheres. ▶ Crystallinity of TiO2 could be improved by B doping. ▶ B doping widens the photo-absorption region and narrows the band gap. ▶ Amounts of superficial hydroxyl groups were increased after boron doping.

The V2O5/SiO2 catalysts promoted by fluoride anion and prepared with different F adding sequences were investigated. The samples were characterized by X-ray photoelectron spectroscopy (XPS), N2 adsorption–desorption, scanning electron microscopy (SEM), X-ray powder diffraction (XRD), temperature-programmed reduction (TPR), oxygen temperature-programmed desorption (O2-TPD) techniques and oxidative dehydrogenation reaction measurements. The results indicated that the fluoride impregnation sequence had a significant effect on the structure and selectivity of propene. Co-impregnation prepared VOF–C catalyst showed a better performance in the ODP reaction. The C3H6 selectivity was 74.9% at 480 °C, compared to 60.9% of V–Si–O sample without promotion. The propane conversion and propene yield were also better. The fluoride addition enhanced the mobility of oxygen in the catalyst.

The 12-phosphotungstic heteropolyacid (HPW) was immobilized on the surface of a silica carrier modified by the amine groups of organosilane γ-aminopropyl triethoxysilane (APTES), and its catalytic performance was investigated for tetrahydrofuran (THF) ring-opening polymerization. This amine-functionalized catalyst exhibited better activity, and the polytetramethylene ether glycol (PTMG) yield was 63.7%. The 12-phosphotungstic heteropolyacid supported on aminopropyl-functionalized SiO2 support (HPW/SiO2-APTES) was reused four times and showed a good maintenance of activity which was better than that of the conventional catalyst HPW supported on SiO2 (HPW/SiO2). These results were obtained using infrared spectroscopy, nuclear magnetic resonance spectroscopy, nitrogen adsorption and X-ray diffraction. HPW on the HPW/SiO2-APTES catalyst exhibited higher dispersed state and maintained a more stable structure than that of the HPW/SiO2 sample.

The over-consumption of fossil fuels resulted in the large quantity emission of carbon dioxide (CO2), which was the main reason for the climate change and more extreme weathers. Hence, it is extremely pressing to explore efficient and sustainable approaches for the carbon-neutral pathway of CO2 utilization and recycling. In our recent works with this context, we developed successfully a novel “chemical vapor deposition integrated process (CVD-IP)” technology to converting robustly CO2 into the value-added solid-form carbon materials. The monometallic FeNi0–Al2O3 (FNi0) and bimetallic FeNix–Al2O3 (FNi2, FNi4, FNi8 and FNi20) samples were synthesized and effective for this new approach. The catalyst labeled FNi8 gave the better performance, exhibited the single pass solid carbon yield of 30%. These results illustrated alternative promising cases for the CO2 capture utilization storage (CCUS), by means of the CO2 catalytic conversion into the solid-form nano carbon materials.Download high-res image (222KB)Download full-size imageThe bimetallic FeNix–Al2O3 (FNi2, FNi4, FNi8 and FNi20) samples were synthesized and effective for CO2 catalytic conversion into the solid-form nano carbon materials with good efficiency.

Two type zirconia (monoclinic and tetragonal phase ZrO2) carriers were synthesized via hydrothermal route, and nano-sized zirconia supported nickel catalysts were prepared by incipient impregnation then followed thermal treatment at 300 °C to 500 °C, for the CO2 selective hydrogenation to synthetic natural gas (SNG). The catalysts were characterized by XRD, CO2-TPD-MS, XPS, TPSR (CH4, CO2) techniques. For comparison, the catalyst NZ-W-400 (monoclinic) synthesized in water solvent exhibited a better catalytic activity than the catalyst NZ-M-400 (tetragonal) prepared in methanol solvent. The catalyst NZ-W-400 displayed more H2 absorbed sites, more basic sites and a lower temperature of initial CO2 activation. Then, the thermal treatment of monoclinic ZrO2 supported nickel precursor was manufactured at three temperature of 350, 400, 500 °C. The TPSR experiments displayed that there were the lower temperature for CO2 activation and initial conversion (185 °C) as well as the lower peak temperature of CH4 generation (318 °C), for the catalyst calcined at 500 °C. This sample contained the more basic sites and the higher catalytic activity, evidenced byCO2-TPD-MS and performance measurement. As for the NZ-W-350 sample, which exhibited the less basic sites and the lower catalytic activity, its initial temperature for CO2 activation and conversion was higher (214 °C) as well as the higher peak temperature of CH4 formation (382 °C).The monoclinic catalyst NZ-W-400/500 exhibited a better catalytic activity than that of tetragonal catalyst NZ-M-400 tetragonal, where the results of TPSR-MS experiments provide the evidences.Download high-res image (184KB)Download full-size image

Copper-promoted nickel-based metal nanoparticles (NPs) with high dispersion and good thermal stability were derived from layered-double hydroxides (LDHs) precursors that were facilely developed by a co-precipitation strategy. The copper-promoted Ni-based metal NPs catalysts were investigated for methane reforming with carbon dioxide to hydrogen and syngas. A series of characterization techniques including XRD, N2 adsorption and desorption, H2-TPR, XPS, CO2-TPD, TEM, TGA and in situ CH4-TPSR were utilized to determine the structure-function relationship for the obtained catalysts. The copper addition accelerated the catalyst reducibility as well as the methane activation, and made the Ni species form smaller NPs during both preparation and reaction by restricting the aggregation. However, with higher copper loading, the derived catalysts were less active during methane reforming with CO2 to syngas. It was confirmed that the catalyst with 1 wt% Cu additive gave the higher catalytic activity and remained stable during long time reaction with excellent resistance to coking and to sintering. Furthermore, the mean size of metal NPs changed minimally from 6.6 to 7.9 nm even after 80 h of time on stream at temperature as high as 700 °C for this optimized catalyst. Therefore, this high dispersed anti-coking copper-promoted nickel catalyst derived from LDHs precursor could be prospective catalyst candidate for the efficient heterogeneous catalysis of sustainable CO2 conversion.Copper-promoted nickel-based metal nanoparticles (NPs) with high dispersion and good thermal stability derived from layered-double hydroxides (LDHs) possessed the enhanced catalytic performance and excellent resistance to sintering and coking for the CO2 reforming of methane.Download high-res image (190KB)Download full-size image

The novel Ni-Ir/γ-Al2O3 catalyst, denoted as NIA-P, was prepared by high-frequency cold plasma direct reduction method under ambient conditions without thermal treatment, and the conventional sample, denoted as NIA-CR, was prepared by impregnation, thermal calcination, and then by H2 reduction method. The effects of reduction methods on the catalysts for ammonia decomposition were studied, and they were characterized by XRD, N2 adsorption, XPS, and H2-TPD. It was found that the plasma-reduced NIA-P sample showed a better catalytic performance, over which ammonia conversion was 68.9%, at T = 450 °C, P = 1 atm, and GHSV = 30, 000 h−1. It was 31.7% higher than that of the conventional NIA-CR sample. XRD results showed that the crystallite size decreased for the sample with plasma reduction, and the dispersion of active components was improved. There were more active components on the surface of the NIA-P sample from the XPS results. This effect resulted in the higher activity for decomposition of ammonia. Meanwhile, the plasma process significantly decreased the time of preparing catalyst.

The density functional theory was used to investigate the adsorption of CH4 and H2O on different rank coal surfaces. The coal rank is the dominant factor in affecting the adsorption capacity of coal. In order to better understand gas and water interaction with coal of different maturity, we developed fourteen coal models to represent the different rank coal. The interactions of CH4 and H2O with coal surfaces were studied and characterized by their adsorption energies, Mulliken charges and electrostatic potential surfaces. The results revealed that the interaction between coal and CH4 was weak physical adsorption, and that the interaction between coal and H2O consisted of physical and chemical adsorption. Adsorption energy of coal–H2O system was larger than that of coal–CH4 on all rank coals, suggesting that the adsorption priority in the coal models is H2O > CH4. Consequently, the injection of H2O into the different rank coal could effectively enhance the coal bed methane (CBM) recovery.Download high-res image (117KB)Download full-size image The adsorption strength of H2O on coal model is stronger than that of CH4 on the same for several rank coal models and the H2O adsorption promotes the CH4 desorption, evidenced using DFT simulations.

Cobalt species and cobalt-support interaction in glow discharge plasma-assisted Fischer–Tropsch catalysts were studied using a combination of characterization techniques (X-ray diffraction, thermo-gravimetric analysis, temperature-programmed reduction, in situ magnetic measurements and in situ X-ray absorption). The catalysts were prepared by incipient impregnation using solutions of cobalt nitrate and ruthenium nitrosyl nitrate followed by plasma or/and oxidative treatment.Cobalt dispersion in silica-supported catalysts was significantly enhanced by plasma pretreatment. Cobalt particle size was a function of glow discharge plasma intensity. The concentration of cobalt silicate in plasma-assisted samples was low. No noticeable effect of the plasma pretreatment on the formation of barely reducible cobalt silicate species was observed. Cobalt reducibility was to some extent hindered in the plasma-assisted catalysts, while promotion with ruthenium significantly enhanced cobalt reducibility in silica-supported catalysts. Due to the combination of high cobalt dispersion and optimized cobalt reducibility, ruthenium-promoted plasma-assisted cobalt catalyst exhibited an enhanced activity in Fischer–Tropsch synthesis.Pretreatment of silica-supported cobalt catalysts with glow discharge plasma leads to smaller cobalt particles without any significant increase in the concentration of barely reducible cobalt silicate. Due to the combination of higher cobalt dispersion and optimized reducibility, ruthenium promoted plasma-assisted cobalt catalyst exhibited an enhanced activity in Fischer–Tropsch synthesis.Download high-res image (78KB)Download full-size image

An easy and efficient method, water-assisted chemical vapor deposition (CVD), was developed to modify multi-walled carbon nanotubes (CNTs) during the CNT growth process. The as-synthesized CNTs with (-H2O) and without (-p) water assistance were explored as ruthenium (Ru) catalyst support for conversion of cellobiose. The Ru/CNTs-H2O catalyst shows much higher conversion of cellobiose (73.6%) and yield of sugar alcohols (39%) than those of Ru/CNTs-p catalyst (28.9% and 21.3%, respectively), which could be ascribed to the highly dispersed Ru nanoparticles due to the presence of oxygen-containing groups and uniform defects on the tube-walls introduced in the water-assisted CVD process.Highlights► Functionalized CNTs (CNTs-H2O) were synthesized by water-assisted CVD. ► Defects and functional groups are introduced onto the walls of CNTs-H2O. ► Ru supported on the CNTs-H2O exhibits high dispersion and utilization efficiency. ► The Ru/CNTs-H2O shows higher cellobiose conversion and sugar alcohol yield.

The morphology and crystal-plane effects of CeO2 materials (nanorods, nanocubes, nanooctas and nanoparticles) on the catalytic performance of Ni/CeO2 in methane dry reforming were investigated. The XRD and Raman results showed that Ni species can be incorporated into the lattices and induce the increase of oxygen vacancies by occupying the vacant sites in the CeO2 nanomaterials. The reaction experiments showed that the catalysts supported over CeO2 nanorods achieved significantly higher catalytic activity and better stability than the other three catalysts. This improved activity was closely related to the strong metal–support interaction between Ni and CeO2 nanorods, which showed great superiority in anchoring Ni nanoparticles. The oxygen vacancies and the mobility of lattice oxygen also showed morphology dependence. They can participate in the catalytic reaction and be favorable for the elimination of carbon deposition. Resistance to carbon deposition was found over the Ni/CeO2-nanorod catalyst, whereas large quantities of graphitic carbon species were formed over the Ni/CeO2-nanocube catalysts, which was responsible for deactivation.

It has been a great challenge to develop an efficient and stable catalyst for dry reforming of methane with carbon dioxide. A new catalyst was synthesized with the catalytically active component in both the lattice and on the surface of the mesoporous support. A remarkable improvement in the catalytic performance of Ni nanocrystals assembled inside pore channels of mesostructured Ni-doped ceria was observed. The initial activity and long-term stability of the sample substantially surpassed that of samples without the intermixed oxide and/or a nonporous architecture, even though the latter was more available. Such an effect concerning a collaborative function stemming from a mesostructure and solid solution has been rarely reported previously in catalysis involving CeO2. We believe that this finding might be of a very generic character and be extended to lots of similar fields. It is expected that the results here can spur experimental and theoretical investigation to promote fundamental comprehension of host–guest or metal–oxide interplay in CeO2-based composite materials.

The synergy between ceria and loaded metal nanocrystals (NCs) greatly promotes the catalytic properties for many reactions. Nevertheless, the clear relevance of structures to properties in catalytic systems is hard to establish in that the catalysts studied either featured unstable microstructures or were too heterogeneous. Herein, we show both the facile tool of NC assembly to derive stable and efficient catalytic materials, in which the metal NCs are tailored in terms of their spatial positioning on the nanometer scale (i.e., entrapped in the internal concave ceria surface or deposited on the external convex ceria surface), and how to probe their structure–function relationship. The performance for producing renewable energy sources from hazardous greenhouse gases on a NCs-in-concavities structure is distinct from that on a NCs-on-convexities configuration, elucidating a pivotal impact by the spatial positioning. The current investigation suggests that there exists a clear relationship between the surface adsorbate bonding strength/type and the catalytic properties in reforming CO2/CH4 to hydrogen energy and syngas. Control over the bonding strength/type and activation mechanism of the adsorbates on the catalyst surfaces through changing the support surface curvature orientation is indicated to be a potential strategy for modulating the reaction activity. The insights focus on grasping the surface chemistry of the ceria surface curvature in optimizing the catalysts and can be enlightening for rationally exploring other state-of-the-art heterogeneous nanomaterials.