In reverse water gas shift （RWGS） reaction COa is converted to CO which in turn can be used to pro- duce beneficial chemicals such as methanol. In the present study, Mo/AlaO3, Fe/AlaO3 and Fe-Mo/Al2O3 catalysts were...In reverse water gas shift （RWGS） reaction COa is converted to CO which in turn can be used to pro- duce beneficial chemicals such as methanol. In the present study, Mo/AlaO3, Fe/AlaO3 and Fe-Mo/Al2O3 catalysts were synthesised using impregnation method. The structures of catalysts were studied using X-ray diffraction （XRD）, Brunauer-Emmett-Teller （BET） method, inductively coupled plasma atomic emission spectrometer （ICP-AES）, temperature programmed reduction （H2-TPR）, CO chemisorption, energy dispersive X-ray （EDX） and scanning electron microscopy （SEM） techniques. Kinetic properties of all catalysts were investigated in a batch re- actor for RWGS reaction. The results indicated that Mo existence in structure of Fe-Mo/AlzO3 catalyst enhances its activity as compared to Fe/AlaO3. This enhancement is probably due to better Fe dispersion and smaller particle size of Fe species. Stability test of Fe-Mo/AlzO3 catalyst was carried out in a fixed bed reactor and a high CO yield for 60 h of time on stream was demonstrated. Fez（MoO4）3 phase was found in the structures of fresh and used catalysts. TPR results also indicate that Fez（MoO4）3 phase has low reducibility, therefore the Fe2（MoO4）3 phase significantly inhibits the reduction of the remaining Fe oxides in the catalyst, resulted in high stability of Fe-Mo/Al2O3 catalyst. Overall, this study introduces Fe-Mo/Al2O3 as a novel catalyst with high CO yield, almost no by-products and fairly stable for RWGS reaction.展开更多
Producing methanol from coke oven gas(COG) is one of the important applications of COG. Removal of sulfur from COG is a key step of this process. Conversion and reaction kinetics over a commercial Fe-Mo/Al2O3 catalyst...Producing methanol from coke oven gas(COG) is one of the important applications of COG. Removal of sulfur from COG is a key step of this process. Conversion and reaction kinetics over a commercial Fe-Mo/Al2O3 catalyst(T-202) were studied in a continuous flow fixed bed reactor under pressures of 1.6-2.8 MPa, space time of 1.32-3.55 s and temperatures of 240-360 °C. Though the COG contains about 0.6 mol/mol H2, hydrogenation of CO and CO2 is not significant on this catalyst. The conversions of unsaturated hydrocarbons depend on their molecular structures. Diolefins and alkynes can be completely hydrogenated even at relatively low temperature and pressure. Olefins, in contrast, can only be progressively hydrogenated with increasing temperature and pressure. The hydrodesulfurization(HDS) of CS2 on this catalyst is easy. Complete conversion of CS2 was observed in the whole range of the conditions used in this work. The original COS in the COG can also be easily converted to a low level. However, its complete HDS is difficult due to the relatively high concentration of CO in the COG and due to the limitation of thermodynamics. H2 S can react with unsaturated hydrocarbons to form ethyl mercaptan and thiophene, which are then progressively hydrodesulfurized with increasing temperature and pressure. Based on the experimental observations, reaction kinetic models for the conversion of ethylene and sulfur-containing compounds were proposed; the values of the parameters in the models were obtained by regression of the experimental data.展开更多
The metal oxide promoter decisively influences the overall performance of Fe catalysts in the direct hydrogenation of CO_(2)to C_(5+)hydrocarbons.However,the roles of metal oxide promoter for Fe catalysts,particularly...The metal oxide promoter decisively influences the overall performance of Fe catalysts in the direct hydrogenation of CO_(2)to C_(5+)hydrocarbons.However,the roles of metal oxide promoter for Fe catalysts,particularly ZrO_(2),have rarely been investigated.To plug this knowledge gap,a new Fe catalyst promoted with Na and partially reduced ZrO_(x)(Na-FeZrO_(x-9))was developed in this study;the catalyst helped produce C_(5+)hydrocarbons in remarkably high yield(26.3%at 360℃).In contrast to ZrO_(x)-free Fe-oxide,NaFeZrO_(x)-9 exhibited long-term stability for CO_(2)hydrogenation(750 h on-stream).The findings revealed multiple roles of ZrO_(x).Notably,ZrO_(x)decorated the Fe-oxide particles after calcination,thereby suppressing excess particle aggregation during the reaction,and acted as a"coke remover"to eliminate the carbon deposited on the catalyst surface.Additionally,oxygen vacancy(O_(v))sites in ZrO_(x)and electron transfer from ZrO_(x)to Fe sites facilitated the adsorption of CO_(2)at the Zr-Fe interface.展开更多
Hanyu Xu 1,Xuedan Song 1,*,Qing Zhang 1,Chang Yu 1,Jieshan Qiu 1,2,*1 Liaoning Key Lab for Energy Materials and Chemical Engineering,State Key Laboratory of Fine Chemicals,School of Chemical Engineering,Dalian Univers...Hanyu Xu 1,Xuedan Song 1,*,Qing Zhang 1,Chang Yu 1,Jieshan Qiu 1,2,*1 Liaoning Key Lab for Energy Materials and Chemical Engineering,State Key Laboratory of Fine Chemicals,School of Chemical Engineering,Dalian University of Technology,Dalian 116024,Liaoning Province,China.展开更多
The nitrogen-coordinated metal single-atom catalysts(M−N−C SACs)with an ultra-high metal loading synthetized by direct high-temperature pyrolysis have been widely reported.However,most of metal single atoms in these c...The nitrogen-coordinated metal single-atom catalysts(M−N−C SACs)with an ultra-high metal loading synthetized by direct high-temperature pyrolysis have been widely reported.However,most of metal single atoms in these catalysts were buried in the carbon matrix,resulting in a low metal utilization and inaccessibility for adsorption of reactants during the catalytic process.Herein,we reported a facile synthesis based on the hard-soft acid-base(HSAB)theory to fabricate Co single-atom catalysts with highly exposed metal atoms ligated to the external pyridinic-N sites of a nitrogen-doped carbon support.Benefiting from the highly accessible Co active sites,the prepared Co−N−C SAC exhibited a superior oxygen reduction reactivity comparable to that of the commercial Pt/C catalyst,showing a high turnover frequency(TOF)of 0.93 e^(−)·s^(-1)·site^(-1)at 0.85 V vs.RHE,far exceeding those of some representative SACs with a ultra-high metal content.This work provides a rational strategy to design and prepare M−N−C single-atom catalysts featured with high site-accessibility and site-density.展开更多
With the development of renewable energy,electrochemical carbon dioxide reduction reaction(CO_(2)RR)has become a potential solution for achieving carbon neutrality.However,until now,due to issues with salt precipitate...With the development of renewable energy,electrochemical carbon dioxide reduction reaction(CO_(2)RR)has become a potential solution for achieving carbon neutrality.However,until now,due to issues with salt precipitate and regeneration of the electrolyte,this technology faces challenges such as difficulty in maintaining long-term stable operation and excessive costs.The pure water CO_(2)electrolyzers are believed to be the ultimate solution to eliminate the salt depreciation and electrolyte issues.This study develops an in-situ method tailored for CO_(2)reduction in pure water.By employing distribution of relaxation times(DRT)analysis and in-situ electrochemical active surface area(ECSA)measurements,we carried out a comprehensive investigation into the mass transport and electrochemical active surface area of gas diffusion electrodes(GDE)under pure water conditions.The maximum 89%CO selectivity and high selectivity(>80%)in the range of 0-300 mA/cm^(2)were achieved using commercial Ag nanoparticles by rational design of catalyst layer.We found that ionomers influence the CO_(2)electrolyzers performance via affecting local pH,GDE-membrane interface,and CO_(2)transport,while catalyst loading mainly influences the active area and CO_(2)transport.This work provides benchmark and insights for future pure water CO_(2)electrolyzers development.展开更多
Metal(oxide)-zeolite bifunctional catalysts have been the subject of considerable attention from researchers in both academic and industry,due to their superior activity and stability in various heterogeneous catalyti...Metal(oxide)-zeolite bifunctional catalysts have been the subject of considerable attention from researchers in both academic and industry,due to their superior activity and stability in various heterogeneous catalytic processes[1–3].Based on the different metal loading sites,these bifunctional catalysts can be categorized as follows:(a)metal species loaded on the outer surface of zeolite crystals,(b)metal species encapsulated within the channels or cavities of zeolites,and(c)metal species incorporated into the zeolite framework(Fig.1).Metal species in type(b)and(c)samples are stabilized by the zeolite frameworks,resulting in excellent thermal and hydrothermal stability during catalytic reactions,especially under harsh conditions,as well as unique shape-selectivity.However,the complex synthesis procedures make large-scale preparation of these catalysts impractical.In contrast,a type(a)sample can be achieved via the simple impregnation;nevertheless,migration of metal species and their aggregation into larger particles often occur during the calcination and reduction processes.展开更多
High-loading Pt/C catalysts play an important role in the fabrication of membrane electrode assemblies with thin catalytic layer,which enhance mass transport and maintain the balance of water and heat.Unfortunately,as...High-loading Pt/C catalysts play an important role in the fabrication of membrane electrode assemblies with thin catalytic layer,which enhance mass transport and maintain the balance of water and heat.Unfortunately,as the loading increases,the agglomeration and growth of Pt nanoparticles(NPs)occur,causing unsatisfactory performance.Here,we present an efficient method for preparing of highly dispersed and small-sized Pt/C catalysts with Pt loadings varying from 39.01 wt%to 66.48 wt%through the high-temperature shock technique.The high density and ultrafine(~2.5 nm)Pt NPs are successfully anchored onto Vulcan XC-72R carbon black without the use of additional capping agents or surfactants.The modified carbon supports enhance the affinity for Pt precursors,contributing to loading efficiencies of 95%or more,while also providing abundant sites for the nucleation and fixation of Pt NPs,thus preventing agglomeration.In the context of the hydrogen evolution reaction in acidic media,the as-synthesized high-loading Pt/C catalysts show remarkable activity and stability,outperforming the state-of-the-art commercial Pt/C.This is mainly because the combined effects of ultrasmall and uniform Pt NPs,optimized electronic structure of Pt site,superhydrophilicity and effective anchoring of Pt NPs.The polymer electrolyte membrane electrolyzer integrated with Pt60/OX72R and commercial IrO2 reaches 1 A cm^(-2)at 1.77 V and operates stably for 120 hours with a negligible voltage decay.This new strategy is fast,scalable and cost-effective for large-scale production of metal-supported catalysts,especially for the high-loading ones.展开更多
Catalytic aryl ether C—O bonds hydrogenolysis was an important route to convert lignite into high valueadded chemicals.Solid super acid 10%Ni-S_(2)O_(8)^(2-)=ZrO_(2) catalysts were successfully synthesized and evalua...Catalytic aryl ether C—O bonds hydrogenolysis was an important route to convert lignite into high valueadded chemicals.Solid super acid 10%Ni-S_(2)O_(8)^(2-)=ZrO_(2) catalysts were successfully synthesized and evaluated their performance in catalytic hydrolysis of lignite derivatives.The excellent performance of 10%Ni-S_(2)O_(8)^(2-)=ZrO_(2) stems from the synergistic interaction between metallic and acidic sites.Specifically,the acidic sites generated by S_(2)O_(8)^(2-) facilitate the adsorption of O atoms in the substrate,whereas the metal sites optimize the process of hydrogen adsorption and activation and promote the generation of hydrogen radicals,which further enhances the ability to break C—O bonds.Thus,10%Ni-S_(2)O_(8)^(2-)=ZrO_(2) exhibits more significantcatalytic activity compared to 10%Ni-ZrO_(2) prepared from pure ZrO_(2) as a support.Characterization results showed that the 10%Ni-S_(2)O_(8)^(2-)=ZrO_(2) catalyst prepared by sodium borohydride reduction method presented a uniform pore structure,which effectively promoted the dispersion of metal Ni on the catalyst surface.Complete conversion of diphenyl ether(DPE)can be achieved under relatively mild conditions,and excellent hydrogenolysis activity is also demonstrated for other lignite derivatives containing C—O bonds.The possible reaction mechanism of DPE hydrogenolysis in the H_(2)-isopropanol system was investigated.This work represents a significantstep forward in the design of highly efficientsolid super acid catalysts.展开更多
Platinum nanoparticles supported on carbons（Pt/C,60%,mass fraction） electrocatalysts for direct methanol fuel cell（DMFC） were prepared by citrate-stabilized method with different reductants and carbon supports.The...Platinum nanoparticles supported on carbons（Pt/C,60%,mass fraction） electrocatalysts for direct methanol fuel cell（DMFC） were prepared by citrate-stabilized method with different reductants and carbon supports.The catalysts were characterized by X-ray diffraction（XRD）,transmission electron microscopy（TEM） and cyclic voltammetry（CV）.It is found that the size of Pt nanoparticles on carbon is controllable by citrate addition and reductant optimization,and the form of carbon support has a great influence on electrocatalytic activity of catalysts.The citrate-stabilized Pt nanoparticles supported on BP2000 carbon,which was reduced by formaldehyde,exhibit the best performance with about 2 nm in diameter and 66.46 m2/g（Pt） in electrocatalytic active surface（EAS） area.Test on single DMFC with 60%（mass fraction） Pt/BP2000 as cathode electrocatalyst showed maximum power density at 78.8 mW/cm2.展开更多
A carbon supported Pd（Pd/C） catalyst used as the anodic catalyst in the direct formic acid fuel cells（DFAFC） was prepared via the improved complex reduction method with sodium ethylenediamine tetracetate（EDTA） a...A carbon supported Pd（Pd/C） catalyst used as the anodic catalyst in the direct formic acid fuel cells（DFAFC） was prepared via the improved complex reduction method with sodium ethylenediamine tetracetate（EDTA） as stabilizer and complexing agent. This method is very simple. The average size of the Pd particles in the Pd/C catalyst prepared with the improved complex reduction method is as small as about 2.1 nm and the Pd particles in the Pd/C catalyst possess an excellent uniformity. The Pd/C catalyst shows a high electrocatalytic activity and stability for the formic acid oxidation.展开更多
Carbon-supported PtPdRuIr, Pd@PtRuIr, PtPd@PtRuIr, and PtPdRu@PtRuIr catalysts were prepared by a colloidal method and their catalytic activities to the methanol oxidation reaction in the acidic media were extensively...Carbon-supported PtPdRuIr, Pd@PtRuIr, PtPd@PtRuIr, and PtPdRu@PtRuIr catalysts were prepared by a colloidal method and their catalytic activities to the methanol oxidation reaction in the acidic media were extensively investigated at room temperature. The catalysts were characterized by transmission electron microscopy and X-ray diffraction techniques, and their electrochemical behavior was evaluated by the cyclic voltammetry. The PtPdRu@PtRuIr/C catalyst is found to yield much higher electrocatalytic activity than the other ones and the commercial catalyst. For example, the Pt metal mass-specific activity of this PtPdRu@PtRuIr/C（Pt content 10 wt%,1.7 mAácm-2ámg-1） electrocatalyst is ＊3-fold higher than that of the commercial JM 40 % Pt/C（0.6 mAácm-2ámg-1）electrocatalysts, and the If/Ib ratio of PtPdRu@PtRuIr/C is1.6, which is higher than that of the JM 40 % Pt/C（0.9）. The improvement may result from the high dispersion of the active metal catalyst and the synergistic effect between the PtRuIr and PtPdRu layers. It is thus concluded that the pseudo-core-shell structure could significantly improve the methanol electro-oxidation activity and CO tolerance of the electrocatalyst.展开更多
It is reported for the first time that the Pt/C catalyst can be prepared with a new and simple organic sol method using SnCl2 as the reductant. It was found that the average size of the Pt particles in the Pt/C cataly...It is reported for the first time that the Pt/C catalyst can be prepared with a new and simple organic sol method using SnCl2 as the reductant. It was found that the average size of the Pt particles in the Pt/C catalysts could be controlled with controlling the preparation conditions. The effect of the average sizes of the Pt particles in the Pt/C catalysts obtained with this method on the electrocatalytical activity of the oxidation of methanol was investigated.展开更多
The effect of acid component including various conventional acids and tungstic compounds on glucose hydrogenation over a series of binary catalyst system containing Ru/C catalyst was investigated. The results showed t...The effect of acid component including various conventional acids and tungstic compounds on glucose hydrogenation over a series of binary catalyst system containing Ru/C catalyst was investigated. The results showed that HC1, H2SO4, H3BO3, H3PO4, and HNO3 had negligible effect, while all the tungstic compounds imposed inhibiting effects on the hydrogenation of glucose over Ru/C catalyst, and the suppressing effect followed the order of H2WO4〉HPW〉WO3〉AMT〉HSiW. This order is the same as the order of ethylene glycol （EG） yields in the one-pot conversion of glucose to EG, suggesting the important role of competition between glucose hydrogenation and retro-aldol condensation in controlling the selectivity of EG.展开更多
Alloying degree, particle size and the level of dispersion are the key structural parameters of Pt-Ru/C catalyst in fuel cells. Solvent（s） used in the preparation process can affect the particle size and alloying de...Alloying degree, particle size and the level of dispersion are the key structural parameters of Pt-Ru/C catalyst in fuel cells. Solvent（s） used in the preparation process can affect the particle size and alloying degree of the object substance, which lead to a great positive impact on its properties. In this work, three types of solvents and their mixtures were used in preparation of the Pt-Ru/C catalysts by chemical reduction of metal precursors with sodium borohydride at room temperature. The structure of the catalysts was characterized by X-ray diffraction （XRD） and Transmission electron microscopy （TEM）. The catalytic activity and stability for methanol electro-oxidation were studied by Cyclic Voltammetry （CV） and Chronoamperometry （CA）. Pt-Ru/C catalyst prepared in H2O or binary solvents of H2O and isopropanol had large particle size and low alloying degree leading to low catalytic activity and less stability in methanol electro-oxidation. When tetrahydrofuran was added to the above solvent systems, Pt-Ru/C catalyst prepared had smaller particle size and higher alloying degree which resulted in better catalytic activity, lower onset and peak potentials, compared with the above catalysts. Moreover, the catalyst prepared in ternary solvents of isopropanol, water and tetrahydrofuran had the smallest particle size, and the high alloying degree and the dispersion kept unchanged. Therefore, this kind of catalyst showed the highest catalytic activity and good stability for methanol electro-oxidation.展开更多
Green and economical CO_(2)utilization is significant for CO_(2)emission reduction and energy development.Here,the 1D Mo_(2)C nanowires with dominant(101)crystal surfaces were modified by the deposition of atomic func...Green and economical CO_(2)utilization is significant for CO_(2)emission reduction and energy development.Here,the 1D Mo_(2)C nanowires with dominant(101)crystal surfaces were modified by the deposition of atomic functional components Rh and K.While unmodifiedβMo_(2)C could only convert CO_(2)to methanol,the designed catalyst of K_(0.2)Rh_(0.2)/β-Mo_(2)C exhibited up to 72.1%of ethanol selectivity at 150℃.It was observed that the atomically dispersed Rh could form the bifunctional active centres with the active carrierβMo_(2)C with the synergistic effects to achieve highly specific controlled C–C coupling.By promoting the CO_(2)adsorption and activation,the introduction of an alkali metal(K)mainly regulated the balanced performance of the two active centres,which in turn improved the hydrogenation selectivity.Overall,the controlled modification ofβMo_(2)C provides a new design strategy for the highly efficient,lowtemperature hydrogenation of CO_(2)to ethanol with single-atom catalysts,which provides an excellent example for the rational design of the complex catalysts.展开更多
Double perovskite-type catalysts including La2 CoMnO6 and La2 CuMnO6 are first evaluated for the effectiveness in removing volatile organic compounds（VOCs）, and single perovskites（La CoO3, LaMnO3, and La Cu O3） ar...Double perovskite-type catalysts including La2 CoMnO6 and La2 CuMnO6 are first evaluated for the effectiveness in removing volatile organic compounds（VOCs）, and single perovskites（La CoO3, LaMnO3, and La Cu O3） are also tested for comparison. All perovskites are tested with the gas hourly space velocity（GHSV） of 30,000 hr^-1, and the temperature range of100–600℃ for C7H8 removal. Experimental results indicate that double perovskites have better activity if compared with single perovskites. Especially, toluene（C7H8） can be completely oxidized to CO2 at 300℃ as La2 Co MnO6 is applied. Characterization of catalysts indicates that double perovskites own unique surface properties and are of higher amounts of lattice oxygen,leading to higher activity. Additionally, apparent activation energy of 68 k J/mol is calculated using Mars-van Krevelen model for C7 H8 oxidation with La2 Co Mn O6 as catalyst. For durability test, both La2 Co Mn O6 and La2 CuMnO6 maintain high C7 H8 removal efficiencies of 100% and98%, respectively, at 300℃ and 30,000 hr^-1, and they also show good resistance to CO2（5%） and H2 O（g）（5%） of the gas streams tested. For various VOCs including isopropyl alcohol（C3H8 O）,ethanal（C2H4O）, and ethylene（C2H4） tested, as high as 100% efficiency could be achieved with double perovskite-type catalysts operated at 300–350℃, indicating that double perovskites are promising catalysts for VOCs removal.展开更多
Catalyst support is extremely important for future fuel cell devices.In this work,we developed doubleshelled C/TiO2(DSCT)hollow spheres as an excellent catalyst support via a template-directed method.The combination o...Catalyst support is extremely important for future fuel cell devices.In this work,we developed doubleshelled C/TiO2(DSCT)hollow spheres as an excellent catalyst support via a template-directed method.The combination of hollow structure,TiO2 shell and carbon layer results in excellent electron conductivity,electrocatalytic activity,and chemical stability.These uniformed DSCT hollow spheres are used as catalyst support to synthesize Pt/DSCT hollow spheres electrocatalyst.The resulting Pt/DSCT hollow spheres exhibited high catalytic performance with a current density of 462 mA mg^-1 for methanol oxidation reaction,which is 2.52 times higher than that of the commercial Pt/C.Furthermore,the increased tolerance to carbonaceous poisoning with a higher If/Ibratio and a better long-term stability in acid media suggests that the DSCT hollow sphere is a promising C/TiO2-based catalyst support for direct methanol fuel cells applications.展开更多
The performance of lignin depolymerization is basically determined by the interunit C–O and C–C bonds.Numerous C–O bond cleavage strategies have been developed, while the cleavage of C–C bond between the primary a...The performance of lignin depolymerization is basically determined by the interunit C–O and C–C bonds.Numerous C–O bond cleavage strategies have been developed, while the cleavage of C–C bond between the primary aromatic units remains a challenging task due to the high dissociation energy of C–C bond.Herein, a multifunctional Ru Re alloy catalyst was designed, which exhibited exceptional catalytic activity for the cleavage of both C–O and C–C linkages in a broad range of lignin model compounds(β-1, a-5, 5–5,β-O-4, 4-O-5) and two stubborn lignins(kraft lignin and alkaline lignin), affording 97.5% overall yield of monocyclic compounds from model compounds and up to 129% of the maximum theoretical yield of monocyclic products based on C–O bonds cleavage from realistic lignin. Scanning transmission electron microscopy(STEM) characterization showed that Ru Re(1:1) alloy particles with hexagonal close-packed structure were homogeneously dispersed on the support. Quasi-in situ X-ray photoelectron spectroscopy(XPS), and X-ray absorption spectroscopy(XAS) indicate that Ru species were predominantly metallic state, whereas Re species were partially oxidized;meanwhile, there was a strong interaction between Ru and Re, where the electron transfer from Re to Ru was occurred, resulting in great improvement on the capability of C–O and C–C bonds cleavage in lignin conversion.展开更多
Atomically dispersed iron-nitrogen-carbon(Fe-N-C) catalysts have emerged as the most promising alternative to the expensive Pt-based catalysts for the oxygen reduction reaction(ORR) in proton exchange membrane fuel ce...Atomically dispersed iron-nitrogen-carbon(Fe-N-C) catalysts have emerged as the most promising alternative to the expensive Pt-based catalysts for the oxygen reduction reaction(ORR) in proton exchange membrane fuel cells(PEMFCs),however suffer from low site density of active Fe-N4 moiety and limited mass transport during the catalytic reaction.To address these challenges,we report a three-dimensional(3D) metal-organic frameworks(MOF)-derived Fe-N-C single-atom catalyst.In this well-designed Fe-N-C catalyst,the micro-scale interconnected skeleton,the nano-scale ordered pores and the atomic-scale abundant carbon edge defects inside the skeleton significantly enhance the site density of active Fe-N4 moiety,thus improving the Fe utilization in the final catalyst.Moreover,the combination of the above mentioned micro-and nano-scale structures greatly facilitates the mass transport in the 3D Fe-N-C catalyst.Therefore,the multiscale engineered Fe-N-C single-atom catalyst achieves excellent ORR performance under acidic condition and affords a significantly enhanced current density and power density in PEMFC.Our findings may open new opportunities for the rational design of FeN-C catalysts through multiscale structural engineering.展开更多
基金Supported by the Iranian Nano Technology Initiative Council and Petroleum University of Technology
文摘In reverse water gas shift （RWGS） reaction COa is converted to CO which in turn can be used to pro- duce beneficial chemicals such as methanol. In the present study, Mo/AlaO3, Fe/AlaO3 and Fe-Mo/Al2O3 catalysts were synthesised using impregnation method. The structures of catalysts were studied using X-ray diffraction （XRD）, Brunauer-Emmett-Teller （BET） method, inductively coupled plasma atomic emission spectrometer （ICP-AES）, temperature programmed reduction （H2-TPR）, CO chemisorption, energy dispersive X-ray （EDX） and scanning electron microscopy （SEM） techniques. Kinetic properties of all catalysts were investigated in a batch re- actor for RWGS reaction. The results indicated that Mo existence in structure of Fe-Mo/AlzO3 catalyst enhances its activity as compared to Fe/AlaO3. This enhancement is probably due to better Fe dispersion and smaller particle size of Fe species. Stability test of Fe-Mo/AlzO3 catalyst was carried out in a fixed bed reactor and a high CO yield for 60 h of time on stream was demonstrated. Fez（MoO4）3 phase was found in the structures of fresh and used catalysts. TPR results also indicate that Fez（MoO4）3 phase has low reducibility, therefore the Fe2（MoO4）3 phase significantly inhibits the reduction of the remaining Fe oxides in the catalyst, resulted in high stability of Fe-Mo/Al2O3 catalyst. Overall, this study introduces Fe-Mo/Al2O3 as a novel catalyst with high CO yield, almost no by-products and fairly stable for RWGS reaction.
文摘Producing methanol from coke oven gas(COG) is one of the important applications of COG. Removal of sulfur from COG is a key step of this process. Conversion and reaction kinetics over a commercial Fe-Mo/Al2O3 catalyst(T-202) were studied in a continuous flow fixed bed reactor under pressures of 1.6-2.8 MPa, space time of 1.32-3.55 s and temperatures of 240-360 °C. Though the COG contains about 0.6 mol/mol H2, hydrogenation of CO and CO2 is not significant on this catalyst. The conversions of unsaturated hydrocarbons depend on their molecular structures. Diolefins and alkynes can be completely hydrogenated even at relatively low temperature and pressure. Olefins, in contrast, can only be progressively hydrogenated with increasing temperature and pressure. The hydrodesulfurization(HDS) of CS2 on this catalyst is easy. Complete conversion of CS2 was observed in the whole range of the conditions used in this work. The original COS in the COG can also be easily converted to a low level. However, its complete HDS is difficult due to the relatively high concentration of CO in the COG and due to the limitation of thermodynamics. H2 S can react with unsaturated hydrocarbons to form ethyl mercaptan and thiophene, which are then progressively hydrodesulfurized with increasing temperature and pressure. Based on the experimental observations, reaction kinetic models for the conversion of ethylene and sulfur-containing compounds were proposed; the values of the parameters in the models were obtained by regression of the experimental data.
基金financial support from the National Research Council of Science&Technology(NST)grant funded by the Ministry of Science and ICT,Republic of Korea(CAP21012-100)the Korea Institute of Energy Technology Evaluation and Planning(KETEP),under the Ministry of Trade,Industry&Energy(MOTIE),Republic of Korea(20224C10300010)the KETEP grant funded by the MOTIE(20224000000440,Sector coupling energy industry advancement manpower training program)。
文摘The metal oxide promoter decisively influences the overall performance of Fe catalysts in the direct hydrogenation of CO_(2)to C_(5+)hydrocarbons.However,the roles of metal oxide promoter for Fe catalysts,particularly ZrO_(2),have rarely been investigated.To plug this knowledge gap,a new Fe catalyst promoted with Na and partially reduced ZrO_(x)(Na-FeZrO_(x-9))was developed in this study;the catalyst helped produce C_(5+)hydrocarbons in remarkably high yield(26.3%at 360℃).In contrast to ZrO_(x)-free Fe-oxide,NaFeZrO_(x)-9 exhibited long-term stability for CO_(2)hydrogenation(750 h on-stream).The findings revealed multiple roles of ZrO_(x).Notably,ZrO_(x)decorated the Fe-oxide particles after calcination,thereby suppressing excess particle aggregation during the reaction,and acted as a"coke remover"to eliminate the carbon deposited on the catalyst surface.Additionally,oxygen vacancy(O_(v))sites in ZrO_(x)and electron transfer from ZrO_(x)to Fe sites facilitated the adsorption of CO_(2)at the Zr-Fe interface.
文摘Hanyu Xu 1,Xuedan Song 1,*,Qing Zhang 1,Chang Yu 1,Jieshan Qiu 1,2,*1 Liaoning Key Lab for Energy Materials and Chemical Engineering,State Key Laboratory of Fine Chemicals,School of Chemical Engineering,Dalian University of Technology,Dalian 116024,Liaoning Province,China.
基金supported by Shanxi Province Science Foundation for Youths(202203021212300)Taiyuan University of Science and Technology Scientific Research Initial Funding(20212064)Outstanding Doctoral Award Fund in Shanxi Province(20222060).
文摘The nitrogen-coordinated metal single-atom catalysts(M−N−C SACs)with an ultra-high metal loading synthetized by direct high-temperature pyrolysis have been widely reported.However,most of metal single atoms in these catalysts were buried in the carbon matrix,resulting in a low metal utilization and inaccessibility for adsorption of reactants during the catalytic process.Herein,we reported a facile synthesis based on the hard-soft acid-base(HSAB)theory to fabricate Co single-atom catalysts with highly exposed metal atoms ligated to the external pyridinic-N sites of a nitrogen-doped carbon support.Benefiting from the highly accessible Co active sites,the prepared Co−N−C SAC exhibited a superior oxygen reduction reactivity comparable to that of the commercial Pt/C catalyst,showing a high turnover frequency(TOF)of 0.93 e^(−)·s^(-1)·site^(-1)at 0.85 V vs.RHE,far exceeding those of some representative SACs with a ultra-high metal content.This work provides a rational strategy to design and prepare M−N−C single-atom catalysts featured with high site-accessibility and site-density.
基金supported by the National Natural Science Foundation of China(No.52394204)by the Shanghai Municipal Science and Technology Major Project。
文摘With the development of renewable energy,electrochemical carbon dioxide reduction reaction(CO_(2)RR)has become a potential solution for achieving carbon neutrality.However,until now,due to issues with salt precipitate and regeneration of the electrolyte,this technology faces challenges such as difficulty in maintaining long-term stable operation and excessive costs.The pure water CO_(2)electrolyzers are believed to be the ultimate solution to eliminate the salt depreciation and electrolyte issues.This study develops an in-situ method tailored for CO_(2)reduction in pure water.By employing distribution of relaxation times(DRT)analysis and in-situ electrochemical active surface area(ECSA)measurements,we carried out a comprehensive investigation into the mass transport and electrochemical active surface area of gas diffusion electrodes(GDE)under pure water conditions.The maximum 89%CO selectivity and high selectivity(>80%)in the range of 0-300 mA/cm^(2)were achieved using commercial Ag nanoparticles by rational design of catalyst layer.We found that ionomers influence the CO_(2)electrolyzers performance via affecting local pH,GDE-membrane interface,and CO_(2)transport,while catalyst loading mainly influences the active area and CO_(2)transport.This work provides benchmark and insights for future pure water CO_(2)electrolyzers development.
基金financially supported by the National Key R&D Program of China(2024YFE0101100)the National Natural Science Foundation of China(22475112,22305132,22305155)+1 种基金the China Postdoctoral Science Foundation(2023M732323)the Postdoctoral Fellowship Program of CPSF(GZC20231679).
文摘Metal(oxide)-zeolite bifunctional catalysts have been the subject of considerable attention from researchers in both academic and industry,due to their superior activity and stability in various heterogeneous catalytic processes[1–3].Based on the different metal loading sites,these bifunctional catalysts can be categorized as follows:(a)metal species loaded on the outer surface of zeolite crystals,(b)metal species encapsulated within the channels or cavities of zeolites,and(c)metal species incorporated into the zeolite framework(Fig.1).Metal species in type(b)and(c)samples are stabilized by the zeolite frameworks,resulting in excellent thermal and hydrothermal stability during catalytic reactions,especially under harsh conditions,as well as unique shape-selectivity.However,the complex synthesis procedures make large-scale preparation of these catalysts impractical.In contrast,a type(a)sample can be achieved via the simple impregnation;nevertheless,migration of metal species and their aggregation into larger particles often occur during the calcination and reduction processes.
文摘High-loading Pt/C catalysts play an important role in the fabrication of membrane electrode assemblies with thin catalytic layer,which enhance mass transport and maintain the balance of water and heat.Unfortunately,as the loading increases,the agglomeration and growth of Pt nanoparticles(NPs)occur,causing unsatisfactory performance.Here,we present an efficient method for preparing of highly dispersed and small-sized Pt/C catalysts with Pt loadings varying from 39.01 wt%to 66.48 wt%through the high-temperature shock technique.The high density and ultrafine(~2.5 nm)Pt NPs are successfully anchored onto Vulcan XC-72R carbon black without the use of additional capping agents or surfactants.The modified carbon supports enhance the affinity for Pt precursors,contributing to loading efficiencies of 95%or more,while also providing abundant sites for the nucleation and fixation of Pt NPs,thus preventing agglomeration.In the context of the hydrogen evolution reaction in acidic media,the as-synthesized high-loading Pt/C catalysts show remarkable activity and stability,outperforming the state-of-the-art commercial Pt/C.This is mainly because the combined effects of ultrasmall and uniform Pt NPs,optimized electronic structure of Pt site,superhydrophilicity and effective anchoring of Pt NPs.The polymer electrolyte membrane electrolyzer integrated with Pt60/OX72R and commercial IrO2 reaches 1 A cm^(-2)at 1.77 V and operates stably for 120 hours with a negligible voltage decay.This new strategy is fast,scalable and cost-effective for large-scale production of metal-supported catalysts,especially for the high-loading ones.
基金supported by the National Key Research and Development Program of China(2022YFB4101100)the National Natural Science Foundation of China(22178375 and 22478414)the Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘Catalytic aryl ether C—O bonds hydrogenolysis was an important route to convert lignite into high valueadded chemicals.Solid super acid 10%Ni-S_(2)O_(8)^(2-)=ZrO_(2) catalysts were successfully synthesized and evaluated their performance in catalytic hydrolysis of lignite derivatives.The excellent performance of 10%Ni-S_(2)O_(8)^(2-)=ZrO_(2) stems from the synergistic interaction between metallic and acidic sites.Specifically,the acidic sites generated by S_(2)O_(8)^(2-) facilitate the adsorption of O atoms in the substrate,whereas the metal sites optimize the process of hydrogen adsorption and activation and promote the generation of hydrogen radicals,which further enhances the ability to break C—O bonds.Thus,10%Ni-S_(2)O_(8)^(2-)=ZrO_(2) exhibits more significantcatalytic activity compared to 10%Ni-ZrO_(2) prepared from pure ZrO_(2) as a support.Characterization results showed that the 10%Ni-S_(2)O_(8)^(2-)=ZrO_(2) catalyst prepared by sodium borohydride reduction method presented a uniform pore structure,which effectively promoted the dispersion of metal Ni on the catalyst surface.Complete conversion of diphenyl ether(DPE)can be achieved under relatively mild conditions,and excellent hydrogenolysis activity is also demonstrated for other lignite derivatives containing C—O bonds.The possible reaction mechanism of DPE hydrogenolysis in the H_(2)-isopropanol system was investigated.This work represents a significantstep forward in the design of highly efficientsolid super acid catalysts.
基金Project(50573041)supported by the National Natural Science Foundation of China
文摘Platinum nanoparticles supported on carbons（Pt/C,60%,mass fraction） electrocatalysts for direct methanol fuel cell（DMFC） were prepared by citrate-stabilized method with different reductants and carbon supports.The catalysts were characterized by X-ray diffraction（XRD）,transmission electron microscopy（TEM） and cyclic voltammetry（CV）.It is found that the size of Pt nanoparticles on carbon is controllable by citrate addition and reductant optimization,and the form of carbon support has a great influence on electrocatalytic activity of catalysts.The citrate-stabilized Pt nanoparticles supported on BP2000 carbon,which was reduced by formaldehyde,exhibit the best performance with about 2 nm in diameter and 66.46 m2/g（Pt） in electrocatalytic active surface（EAS） area.Test on single DMFC with 60%（mass fraction） Pt/BP2000 as cathode electrocatalyst showed maximum power density at 78.8 mW/cm2.
基金Supported by the "863" Program of Science and Technology Ministry of China(Nos.2006AA05Z137, 2007AA05Z143 and 2007AA05Z159)National Natural Science Foundation of China(Nos.20433060, 20473038, 20573057 and 20703043)the Natural Science Foundation of Jiangsu Province, China(No.BK2006224).
文摘A carbon supported Pd（Pd/C） catalyst used as the anodic catalyst in the direct formic acid fuel cells（DFAFC） was prepared via the improved complex reduction method with sodium ethylenediamine tetracetate（EDTA） as stabilizer and complexing agent. This method is very simple. The average size of the Pd particles in the Pd/C catalyst prepared with the improved complex reduction method is as small as about 2.1 nm and the Pd particles in the Pd/C catalyst possess an excellent uniformity. The Pd/C catalyst shows a high electrocatalytic activity and stability for the formic acid oxidation.
基金financially supported by the National Natural Scientific Foundation of China (Nos. 20673040 and20876062)Guangdong Provincial Scientific Foundation (Nos. 36055 and S2012040007383)the Key Laboratory of Fuel Cell Technology of Guangdong Province (No. 201112)
文摘Carbon-supported PtPdRuIr, Pd@PtRuIr, PtPd@PtRuIr, and PtPdRu@PtRuIr catalysts were prepared by a colloidal method and their catalytic activities to the methanol oxidation reaction in the acidic media were extensively investigated at room temperature. The catalysts were characterized by transmission electron microscopy and X-ray diffraction techniques, and their electrochemical behavior was evaluated by the cyclic voltammetry. The PtPdRu@PtRuIr/C catalyst is found to yield much higher electrocatalytic activity than the other ones and the commercial catalyst. For example, the Pt metal mass-specific activity of this PtPdRu@PtRuIr/C（Pt content 10 wt%,1.7 mAácm-2ámg-1） electrocatalyst is ＊3-fold higher than that of the commercial JM 40 % Pt/C（0.6 mAácm-2ámg-1）electrocatalysts, and the If/Ib ratio of PtPdRu@PtRuIr/C is1.6, which is higher than that of the JM 40 % Pt/C（0.9）. The improvement may result from the high dispersion of the active metal catalyst and the synergistic effect between the PtRuIr and PtPdRu layers. It is thus concluded that the pseudo-core-shell structure could significantly improve the methanol electro-oxidation activity and CO tolerance of the electrocatalyst.
文摘It is reported for the first time that the Pt/C catalyst can be prepared with a new and simple organic sol method using SnCl2 as the reductant. It was found that the average size of the Pt particles in the Pt/C catalysts could be controlled with controlling the preparation conditions. The effect of the average sizes of the Pt particles in the Pt/C catalysts obtained with this method on the electrocatalytical activity of the oxidation of methanol was investigated.
基金supported by the National Natural Science Foundation of China(Grants 21176235 and 21206159)
文摘The effect of acid component including various conventional acids and tungstic compounds on glucose hydrogenation over a series of binary catalyst system containing Ru/C catalyst was investigated. The results showed that HC1, H2SO4, H3BO3, H3PO4, and HNO3 had negligible effect, while all the tungstic compounds imposed inhibiting effects on the hydrogenation of glucose over Ru/C catalyst, and the suppressing effect followed the order of H2WO4〉HPW〉WO3〉AMT〉HSiW. This order is the same as the order of ethylene glycol （EG） yields in the one-pot conversion of glucose to EG, suggesting the important role of competition between glucose hydrogenation and retro-aldol condensation in controlling the selectivity of EG.
基金supported by 863 Project(No.2006AA05Z102)the Cultivation Fund of the Key Scientific and Technical Innovation Project,Ministry of Education of China (No.707050)+1 种基金Specialized Research Fund for the Doctoral Program of Higher Education (No.20060610023)Chengdu Natural Science Foundation (Nos.06GGYB449GX-030,and 07GGZD139GX)
文摘Alloying degree, particle size and the level of dispersion are the key structural parameters of Pt-Ru/C catalyst in fuel cells. Solvent（s） used in the preparation process can affect the particle size and alloying degree of the object substance, which lead to a great positive impact on its properties. In this work, three types of solvents and their mixtures were used in preparation of the Pt-Ru/C catalysts by chemical reduction of metal precursors with sodium borohydride at room temperature. The structure of the catalysts was characterized by X-ray diffraction （XRD） and Transmission electron microscopy （TEM）. The catalytic activity and stability for methanol electro-oxidation were studied by Cyclic Voltammetry （CV） and Chronoamperometry （CA）. Pt-Ru/C catalyst prepared in H2O or binary solvents of H2O and isopropanol had large particle size and low alloying degree leading to low catalytic activity and less stability in methanol electro-oxidation. When tetrahydrofuran was added to the above solvent systems, Pt-Ru/C catalyst prepared had smaller particle size and higher alloying degree which resulted in better catalytic activity, lower onset and peak potentials, compared with the above catalysts. Moreover, the catalyst prepared in ternary solvents of isopropanol, water and tetrahydrofuran had the smallest particle size, and the high alloying degree and the dispersion kept unchanged. Therefore, this kind of catalyst showed the highest catalytic activity and good stability for methanol electro-oxidation.
基金financially supported by the National Natural Science Foundation of China(21925803,U19A2015)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB36030200)the Liao Ning Revitalization Talents Program(XLYC1907170).
文摘Green and economical CO_(2)utilization is significant for CO_(2)emission reduction and energy development.Here,the 1D Mo_(2)C nanowires with dominant(101)crystal surfaces were modified by the deposition of atomic functional components Rh and K.While unmodifiedβMo_(2)C could only convert CO_(2)to methanol,the designed catalyst of K_(0.2)Rh_(0.2)/β-Mo_(2)C exhibited up to 72.1%of ethanol selectivity at 150℃.It was observed that the atomically dispersed Rh could form the bifunctional active centres with the active carrierβMo_(2)C with the synergistic effects to achieve highly specific controlled C–C coupling.By promoting the CO_(2)adsorption and activation,the introduction of an alkali metal(K)mainly regulated the balanced performance of the two active centres,which in turn improved the hydrogenation selectivity.Overall,the controlled modification ofβMo_(2)C provides a new design strategy for the highly efficient,lowtemperature hydrogenation of CO_(2)to ethanol with single-atom catalysts,which provides an excellent example for the rational design of the complex catalysts.
基金the Ministry of Science and Technology(MOST),Republic of China(ROC)(No.102WFA0700516)National Central University(No.105G910-9)for fundingfinancial support from the Industrial Technology Research Institute(No.105G910-8)
文摘Double perovskite-type catalysts including La2 CoMnO6 and La2 CuMnO6 are first evaluated for the effectiveness in removing volatile organic compounds（VOCs）, and single perovskites（La CoO3, LaMnO3, and La Cu O3） are also tested for comparison. All perovskites are tested with the gas hourly space velocity（GHSV） of 30,000 hr^-1, and the temperature range of100–600℃ for C7H8 removal. Experimental results indicate that double perovskites have better activity if compared with single perovskites. Especially, toluene（C7H8） can be completely oxidized to CO2 at 300℃ as La2 Co MnO6 is applied. Characterization of catalysts indicates that double perovskites own unique surface properties and are of higher amounts of lattice oxygen,leading to higher activity. Additionally, apparent activation energy of 68 k J/mol is calculated using Mars-van Krevelen model for C7 H8 oxidation with La2 Co Mn O6 as catalyst. For durability test, both La2 Co Mn O6 and La2 CuMnO6 maintain high C7 H8 removal efficiencies of 100% and98%, respectively, at 300℃ and 30,000 hr^-1, and they also show good resistance to CO2（5%） and H2 O（g）（5%） of the gas streams tested. For various VOCs including isopropyl alcohol（C3H8 O）,ethanal（C2H4O）, and ethylene（C2H4） tested, as high as 100% efficiency could be achieved with double perovskite-type catalysts operated at 300–350℃, indicating that double perovskites are promising catalysts for VOCs removal.
基金supported by the Scholarship from China Scholarship Council(CSC)(Grant no.201604910621)。
文摘Catalyst support is extremely important for future fuel cell devices.In this work,we developed doubleshelled C/TiO2(DSCT)hollow spheres as an excellent catalyst support via a template-directed method.The combination of hollow structure,TiO2 shell and carbon layer results in excellent electron conductivity,electrocatalytic activity,and chemical stability.These uniformed DSCT hollow spheres are used as catalyst support to synthesize Pt/DSCT hollow spheres electrocatalyst.The resulting Pt/DSCT hollow spheres exhibited high catalytic performance with a current density of 462 mA mg^-1 for methanol oxidation reaction,which is 2.52 times higher than that of the commercial Pt/C.Furthermore,the increased tolerance to carbonaceous poisoning with a higher If/Ibratio and a better long-term stability in acid media suggests that the DSCT hollow sphere is a promising C/TiO2-based catalyst support for direct methanol fuel cells applications.
基金The National Natural Science Foundation of China(22078317,21878288,21721004,21690083)。
文摘The performance of lignin depolymerization is basically determined by the interunit C–O and C–C bonds.Numerous C–O bond cleavage strategies have been developed, while the cleavage of C–C bond between the primary aromatic units remains a challenging task due to the high dissociation energy of C–C bond.Herein, a multifunctional Ru Re alloy catalyst was designed, which exhibited exceptional catalytic activity for the cleavage of both C–O and C–C linkages in a broad range of lignin model compounds(β-1, a-5, 5–5,β-O-4, 4-O-5) and two stubborn lignins(kraft lignin and alkaline lignin), affording 97.5% overall yield of monocyclic compounds from model compounds and up to 129% of the maximum theoretical yield of monocyclic products based on C–O bonds cleavage from realistic lignin. Scanning transmission electron microscopy(STEM) characterization showed that Ru Re(1:1) alloy particles with hexagonal close-packed structure were homogeneously dispersed on the support. Quasi-in situ X-ray photoelectron spectroscopy(XPS), and X-ray absorption spectroscopy(XAS) indicate that Ru species were predominantly metallic state, whereas Re species were partially oxidized;meanwhile, there was a strong interaction between Ru and Re, where the electron transfer from Re to Ru was occurred, resulting in great improvement on the capability of C–O and C–C bonds cleavage in lignin conversion.
基金supported by the National Natural Science Foundation of China(51722103,52071231 and 51571149)the Natural Science Foundation of Tianjin City(19JCJQJC61900)。
文摘Atomically dispersed iron-nitrogen-carbon(Fe-N-C) catalysts have emerged as the most promising alternative to the expensive Pt-based catalysts for the oxygen reduction reaction(ORR) in proton exchange membrane fuel cells(PEMFCs),however suffer from low site density of active Fe-N4 moiety and limited mass transport during the catalytic reaction.To address these challenges,we report a three-dimensional(3D) metal-organic frameworks(MOF)-derived Fe-N-C single-atom catalyst.In this well-designed Fe-N-C catalyst,the micro-scale interconnected skeleton,the nano-scale ordered pores and the atomic-scale abundant carbon edge defects inside the skeleton significantly enhance the site density of active Fe-N4 moiety,thus improving the Fe utilization in the final catalyst.Moreover,the combination of the above mentioned micro-and nano-scale structures greatly facilitates the mass transport in the 3D Fe-N-C catalyst.Therefore,the multiscale engineered Fe-N-C single-atom catalyst achieves excellent ORR performance under acidic condition and affords a significantly enhanced current density and power density in PEMFC.Our findings may open new opportunities for the rational design of FeN-C catalysts through multiscale structural engineering.
