Metastable molybdenum carbide(α-MoC),as a catalyst and an excellent support for metal catalysts,has been widely used in thermo/electro-catalytic reactions.However,the selective synthesis ofα-MoC remains a great chal...Metastable molybdenum carbide(α-MoC),as a catalyst and an excellent support for metal catalysts,has been widely used in thermo/electro-catalytic reactions.However,the selective synthesis ofα-MoC remains a great challenge.Herein,a simple one-pot synthetic strategy for the selective preparation of metastableα-MoC is proposed by electrochemical co-reduction of CO_(2)and MoO_(3)in a low-temperature eutectic molten carbonate.The synthesizedα-MoC shows a reed flower-like morphology.By controlling the electrolysis time and monitoring the phase and morphology of the obtained products,the growth process ofα-MoC is revealed,where the carbon matrix is deposited first followed by the growth ofα-MoC from the carbon matrix.Moreover,by analyzing the composition of the electrolytic products,the formation mechanism forα-MoC is proposed.In addition,through this one-pot synthetic strategy,S-dopedα-MoC is successfully synthesized.Density functional theory(DFT)calculations reveal that S doping enhanced the HER performance ofα-MoC by facilitating water absorption and dissociation and weakening the bond energy of Mo-H to accelerate H desorption.The present work not only highlights the valuable utilization of CO_(2) but also offers a new perspective on the design and controllable synthesis of metal carbides and their derivatives.展开更多
Catalytic selective hydrogenation of alkynes to the corresponding alkenes is an important process in industrial production.Modulating the selective hydrogenation of alkynes to the alkenes requires ingenuity since alke...Catalytic selective hydrogenation of alkynes to the corresponding alkenes is an important process in industrial production.Modulating the selective hydrogenation of alkynes to the alkenes requires ingenuity since alkenes can easily be converted into the corresponding alkanes under reductive conditions.Applying different reductive reagents to prevent the direct usage of H_(2)can avoid difficulties in hydrogen storage and transportation.Herein,we demonstrate a tandem process to hydrogenate phenylacetylene by CO and H_(2)Oviathecouplingof thelow-temperaturewater-gas shift reaction and selective hydrogenation of phenylacetylene utilizing theα-MoC catalyst.The reductive reagent,CO,not only produces H_(2)from H_(2)O to drive the reaction forward,but it also regulates the selectivity of styrene by preventing further hydrogenation.展开更多
In this work,we investigated the methanol steam reforming(MSR)reaction(CH_(3)OH+H_(2)O→CO_(2)+3H_(2))catalyzed byα-MoC by means of density functional theory calculations.The adsorption behavior of the relevant inter...In this work,we investigated the methanol steam reforming(MSR)reaction(CH_(3)OH+H_(2)O→CO_(2)+3H_(2))catalyzed byα-MoC by means of density functional theory calculations.The adsorption behavior of the relevant intermediates and the kinetics of the elementary steps in the MSR reaction are systematically investigated.The results show that,on theα-MoC(100)surface,the O−H bond cleavage of CH3OH leads to CH3O,which subsequently dehydrogenates to CH_(2)O.Then,the formation of CH_(2)OOH between CH_(2)O and OH is favored over the decomposition to CHO and H.The sequential dehydrogenation of CH_(2)OOH results in a high selectivity for CO_(2).In contrast,the over-strong adsorption of the CH_(2)O intermediate on theα-MoC(111)surface leads to its dehydrogenation to CO product.In addition,we found that OH species,which is produced from the facile water activation,help the O−H bond breaking of intermediates by lowering the reaction energy barrier.This work not only reveals the catalytic role played byα-MoC(100)in the MSR reaction,but also provides theoretical guidance for the design ofα-MoC-based catalysts.展开更多
Oxide supports modify electronic structures of supported metal nanoparticles,and then affect the catalytic activity associated with the so-called strong metal-support interaction(SMSI).We herein report the strong infl...Oxide supports modify electronic structures of supported metal nanoparticles,and then affect the catalytic activity associated with the so-called strong metal-support interaction(SMSI).We herein report the strong influence of SMSI employing Ni_(4)/α-MoC(111) and defective Ni_(4)/MgO(100) catalysts used for dry reforming of methane(DRM,CO_(2)+CH_4→2 CO+2 H_(2)) by using density functional theory(DFT) and kinetic Monte Carlo simulation(KMC).The results show that α-MoC(111) and MgO(100) surface have converse electron and structural effect for Ni_(4) cluster.The electrons transfer from a-MoC(111) surface to Ni atoms,but electrons transfer from Ni atoms to MgO(100) surface;an extensive tensile strain is greatly released in the Ni lattice by MgO,but the extensive tensile strain is introduced in the Ni lattice by α-MoC.As a result,although both catalysts show good stability,H_(2)/CO ratio on Ni_(4)/α-MoC(111) is obviously larger than that on Ni_(4)/MgO(100).The result shows that Ni/α-MoC is a good catalyst for DRM reaction comparing with Ni/MgO catalyst.展开更多
The α phase Mo carbide has been widely investigated recently for its high activity in hydrogen production from water gas shift (WGS) reaction. However, high loading of noble metals as well as high economic and enviro...The α phase Mo carbide has been widely investigated recently for its high activity in hydrogen production from water gas shift (WGS) reaction. However, high loading of noble metals as well as high economic and environmental cost derived from high-temperature ammonification and carbonization process will lead to high cost of hydrogen production. Thus, the efficient controlling of phase transfer is promising. Herein, metals (Au, Pt, Rh, Cu) with a wide range of loadings were impregnated on flame spray pyrolysis (FSP) made MoO_(3) to produce Mo carbides by one-step carbonization. A breakthrough high metal-normalized hydrogen production rate of 213 mmol H2·gmetal^(-1)·s^(-1) was achieved on 0.025 wt% Rh/MoCx, which was much higher than Pt and Au based Mo carbides ever reported. The addition of trace Rh induced direct MoO_(3) transformation to high purity α-MoC_(1-x) in one-step carbonization instead of two-steps ammonification and carbonization process. In comparison to Rh, the addition of Pt, Au and Cu tend to transfer MoO_(3) into β-Mo2C at the same conditions. Besides, the one with 2 wt% Rh exhibited high stability in WGS reaction even at high temperature (300 ℃) due to its inhibition on carbides oxidation induced by H2O. We demonstrate that it is feasible to control phase transfer of Mo carbides even by trace amount of metals to simplify the production process of catalysts. The catalytic performance improved by Rh in aspects of both activity and stability provides a guide for producing more stable Mo carbides catalysts.展开更多
基金the financial support from National Natural Science Foundation of China(Nos.22071070,21971077).
文摘Metastable molybdenum carbide(α-MoC),as a catalyst and an excellent support for metal catalysts,has been widely used in thermo/electro-catalytic reactions.However,the selective synthesis ofα-MoC remains a great challenge.Herein,a simple one-pot synthetic strategy for the selective preparation of metastableα-MoC is proposed by electrochemical co-reduction of CO_(2)and MoO_(3)in a low-temperature eutectic molten carbonate.The synthesizedα-MoC shows a reed flower-like morphology.By controlling the electrolysis time and monitoring the phase and morphology of the obtained products,the growth process ofα-MoC is revealed,where the carbon matrix is deposited first followed by the growth ofα-MoC from the carbon matrix.Moreover,by analyzing the composition of the electrolytic products,the formation mechanism forα-MoC is proposed.In addition,through this one-pot synthetic strategy,S-dopedα-MoC is successfully synthesized.Density functional theory(DFT)calculations reveal that S doping enhanced the HER performance ofα-MoC by facilitating water absorption and dissociation and weakening the bond energy of Mo-H to accelerate H desorption.The present work not only highlights the valuable utilization of CO_(2) but also offers a new perspective on the design and controllable synthesis of metal carbides and their derivatives.
基金the Natural Science Foundation of China(grant nos.21725301,21932002,and 21821004)the National Key R&D Program of China(grant no.2021YFA1501102)China Petrochemical Corporation(grant no.420043-10).
文摘Catalytic selective hydrogenation of alkynes to the corresponding alkenes is an important process in industrial production.Modulating the selective hydrogenation of alkynes to the alkenes requires ingenuity since alkenes can easily be converted into the corresponding alkanes under reductive conditions.Applying different reductive reagents to prevent the direct usage of H_(2)can avoid difficulties in hydrogen storage and transportation.Herein,we demonstrate a tandem process to hydrogenate phenylacetylene by CO and H_(2)Oviathecouplingof thelow-temperaturewater-gas shift reaction and selective hydrogenation of phenylacetylene utilizing theα-MoC catalyst.The reductive reagent,CO,not only produces H_(2)from H_(2)O to drive the reaction forward,but it also regulates the selectivity of styrene by preventing further hydrogenation.
基金This work is supported by the National Natural Science Foundation of China(No.21973013)the National Natural Science Foundation of Fujian Province,China(No.2020J02025)the“Chuying Program”for the Top Young Talents of Fujian Province.Numerical computations were performed on Hefei Advanced Computing Center.
文摘In this work,we investigated the methanol steam reforming(MSR)reaction(CH_(3)OH+H_(2)O→CO_(2)+3H_(2))catalyzed byα-MoC by means of density functional theory calculations.The adsorption behavior of the relevant intermediates and the kinetics of the elementary steps in the MSR reaction are systematically investigated.The results show that,on theα-MoC(100)surface,the O−H bond cleavage of CH3OH leads to CH3O,which subsequently dehydrogenates to CH_(2)O.Then,the formation of CH_(2)OOH between CH_(2)O and OH is favored over the decomposition to CHO and H.The sequential dehydrogenation of CH_(2)OOH results in a high selectivity for CO_(2).In contrast,the over-strong adsorption of the CH_(2)O intermediate on theα-MoC(111)surface leads to its dehydrogenation to CO product.In addition,we found that OH species,which is produced from the facile water activation,help the O−H bond breaking of intermediates by lowering the reaction energy barrier.This work not only reveals the catalytic role played byα-MoC(100)in the MSR reaction,but also provides theoretical guidance for the design ofα-MoC-based catalysts.
基金the National Natural Science Foundation of China (21776197 and 21776195)Shanxi Province Science Foundation for Youths (201701D211003)Key Research and Development Program of Shanxi Province (International Cooperation, 201903D421074) for their financial support。
文摘Oxide supports modify electronic structures of supported metal nanoparticles,and then affect the catalytic activity associated with the so-called strong metal-support interaction(SMSI).We herein report the strong influence of SMSI employing Ni_(4)/α-MoC(111) and defective Ni_(4)/MgO(100) catalysts used for dry reforming of methane(DRM,CO_(2)+CH_4→2 CO+2 H_(2)) by using density functional theory(DFT) and kinetic Monte Carlo simulation(KMC).The results show that α-MoC(111) and MgO(100) surface have converse electron and structural effect for Ni_(4) cluster.The electrons transfer from a-MoC(111) surface to Ni atoms,but electrons transfer from Ni atoms to MgO(100) surface;an extensive tensile strain is greatly released in the Ni lattice by MgO,but the extensive tensile strain is introduced in the Ni lattice by α-MoC.As a result,although both catalysts show good stability,H_(2)/CO ratio on Ni_(4)/α-MoC(111) is obviously larger than that on Ni_(4)/MgO(100).The result shows that Ni/α-MoC is a good catalyst for DRM reaction comparing with Ni/MgO catalyst.
基金This study was supported by DICP(Grant:DICP 1202012)the Natural Science Foundation of China(22078315)+1 种基金the LiaoNing Revitalization Talents Program(XLYC1907066)the Youth Innovation Promotion Association of Chinese Academy of Sciences(2018214).
文摘The α phase Mo carbide has been widely investigated recently for its high activity in hydrogen production from water gas shift (WGS) reaction. However, high loading of noble metals as well as high economic and environmental cost derived from high-temperature ammonification and carbonization process will lead to high cost of hydrogen production. Thus, the efficient controlling of phase transfer is promising. Herein, metals (Au, Pt, Rh, Cu) with a wide range of loadings were impregnated on flame spray pyrolysis (FSP) made MoO_(3) to produce Mo carbides by one-step carbonization. A breakthrough high metal-normalized hydrogen production rate of 213 mmol H2·gmetal^(-1)·s^(-1) was achieved on 0.025 wt% Rh/MoCx, which was much higher than Pt and Au based Mo carbides ever reported. The addition of trace Rh induced direct MoO_(3) transformation to high purity α-MoC_(1-x) in one-step carbonization instead of two-steps ammonification and carbonization process. In comparison to Rh, the addition of Pt, Au and Cu tend to transfer MoO_(3) into β-Mo2C at the same conditions. Besides, the one with 2 wt% Rh exhibited high stability in WGS reaction even at high temperature (300 ℃) due to its inhibition on carbides oxidation induced by H2O. We demonstrate that it is feasible to control phase transfer of Mo carbides even by trace amount of metals to simplify the production process of catalysts. The catalytic performance improved by Rh in aspects of both activity and stability provides a guide for producing more stable Mo carbides catalysts.
