A series of Ru/FeOx catalysts were synthesized for the selective hydrogenation of CO2to CO.Detailed characterizations of the catalysts through X‐ray diffraction,X‐ray photoelectron spectroscopy,transmission electron...A series of Ru/FeOx catalysts were synthesized for the selective hydrogenation of CO2to CO.Detailed characterizations of the catalysts through X‐ray diffraction,X‐ray photoelectron spectroscopy,transmission electron microscopy,and temperature‐programmed techniques were performed to directly monitor the surface chemical properties and the catalytic performance to elucidate the reaction mechanism.Highly dispersed Ru species were observed on the surface of FeOx regardless of the initial Ru loading.Varying the Ru loading resulted in changes to the Ru coverage over the FeOx surface,which had a significant impact on the interaction between Ru and adsorbed H,and concomitantly,the H2activation capacity via the ability for H2dissociation.FeOx having0.01%of Ru loading exhibited100%selectivity toward CO resulting from the very strong interaction between Ru and adsorbed H,which limits the desorption of the activated H species and hinders over‐reduction of CO to CH4.Further increasing the Ru loading of the catalysts to above0.01%resulted in the adsorbed H to be easily dissociated,as a result of a weaker interaction with Ru,which allowed excessive CO reduction to produce CH4.Understanding how to selectively design the catalyst by tuning the initial loading of the active phase has broader implications on the design of supported metal catalysts toward preparing liquid fuels from CO2.?2018,Dalian Institute of Chemical Physics,Chinese Academy of Sciences toward preparing liquid fuels from CO2.?2018,Dalian Institute of Chemical Physics,Chinese Academy of Sciences.Published by Elsevier B.V.All rights reserved.展开更多
The study of the hydrogen evolution reaction(HER)aimed to reach a deeper understanding of the parameters that control the rate of this reaction is of great importance given the technical relevance of hydrogen producti...The study of the hydrogen evolution reaction(HER)aimed to reach a deeper understanding of the parameters that control the rate of this reaction is of great importance given the technical relevance of hydrogen production as an energy vector in the so-called hydrogen economy.In previous works,laser-induced temperature jump(LITJ)experiments on Pt(111)modified with Ni(OH)_(2)in alkaline media have revealed the importance of the interfacial electric field in the rate of the HER.It was hypothesised that small amounts of Ni(OH)_(2)cause a decrease of the electric field because of a negative shift of the pzfc toward the onset of the hydrogen evolution.In this work,to test the validity of this hypothesis,the study has been extended to Pt(111)surfaces modified with Fe(OH)_(2).The modified surfaces have been studied voltammetrically,and the voltammetric charges have been analysed.The voltammograms show a peak in the hydrogen evolution region that suggest the transformation in the adlayer from Fe(II)to Fe(0).In agreement with the coulometric analysis,the voltammetric features in the OH adsorption region would be related with the oxidation to the+3 valence state.The results obtained with LITJ method reflect the existence of a strong interaction of the Fe oxophilic species with the water molecules,shifting the potential of maximum entropy away from the onset of the HER.Hence,the most catalytic surface is the one with the lowest Fe coverage.展开更多
Using molecular dynamics （MD） simulations, we have investigated the kinetics of the graphene edge folding process. The lower limit of the energy barrier is found to be -380 meV/A （or about 800 meV per edge atom） a...Using molecular dynamics （MD） simulations, we have investigated the kinetics of the graphene edge folding process. The lower limit of the energy barrier is found to be -380 meV/A （or about 800 meV per edge atom） and -50 meV/A （or about 120 meV per edge atom） for folding the edges of intrinsic clean single-layer graphene （SLG） and double-layer graphene （DLG）, respectively. However, the edge folding barriers can be substantially reduced by imbalanced chemical adsorption, such as of H atoms, on the two sides of graphene along the edges. Our studies indicate that thermal folding is not feasible at room temperature （RT） for clean SLG and DLG edges and is feasible at high temperature only for DLG edges, whereas chemical folding （with adsorbates） of both SLG and DLG edges can be spontaneous at RT. These findings suggest that the folded edge structures of suspended graphene observed in some experiments are possibly due to the presence of adsorbates at the edges.展开更多
基金supported by the National Natural Science Foundation of China(21476145,91645117)China Postdoctoral Science Foundation(2016M600221)~~
文摘A series of Ru/FeOx catalysts were synthesized for the selective hydrogenation of CO2to CO.Detailed characterizations of the catalysts through X‐ray diffraction,X‐ray photoelectron spectroscopy,transmission electron microscopy,and temperature‐programmed techniques were performed to directly monitor the surface chemical properties and the catalytic performance to elucidate the reaction mechanism.Highly dispersed Ru species were observed on the surface of FeOx regardless of the initial Ru loading.Varying the Ru loading resulted in changes to the Ru coverage over the FeOx surface,which had a significant impact on the interaction between Ru and adsorbed H,and concomitantly,the H2activation capacity via the ability for H2dissociation.FeOx having0.01%of Ru loading exhibited100%selectivity toward CO resulting from the very strong interaction between Ru and adsorbed H,which limits the desorption of the activated H species and hinders over‐reduction of CO to CH4.Further increasing the Ru loading of the catalysts to above0.01%resulted in the adsorbed H to be easily dissociated,as a result of a weaker interaction with Ru,which allowed excessive CO reduction to produce CH4.Understanding how to selectively design the catalyst by tuning the initial loading of the active phase has broader implications on the design of supported metal catalysts toward preparing liquid fuels from CO2.?2018,Dalian Institute of Chemical Physics,Chinese Academy of Sciences toward preparing liquid fuels from CO2.?2018,Dalian Institute of Chemical Physics,Chinese Academy of Sciences.Published by Elsevier B.V.All rights reserved.
基金funded by Ministerio de Ciencia e Innovación (Spain) (PID2019-105653GB-I00)Generalitat Valenciana (Spain) (PROMETEO/2020/063)。
文摘The study of the hydrogen evolution reaction(HER)aimed to reach a deeper understanding of the parameters that control the rate of this reaction is of great importance given the technical relevance of hydrogen production as an energy vector in the so-called hydrogen economy.In previous works,laser-induced temperature jump(LITJ)experiments on Pt(111)modified with Ni(OH)_(2)in alkaline media have revealed the importance of the interfacial electric field in the rate of the HER.It was hypothesised that small amounts of Ni(OH)_(2)cause a decrease of the electric field because of a negative shift of the pzfc toward the onset of the hydrogen evolution.In this work,to test the validity of this hypothesis,the study has been extended to Pt(111)surfaces modified with Fe(OH)_(2).The modified surfaces have been studied voltammetrically,and the voltammetric charges have been analysed.The voltammograms show a peak in the hydrogen evolution region that suggest the transformation in the adlayer from Fe(II)to Fe(0).In agreement with the coulometric analysis,the voltammetric features in the OH adsorption region would be related with the oxidation to the+3 valence state.The results obtained with LITJ method reflect the existence of a strong interaction of the Fe oxophilic species with the water molecules,shifting the potential of maximum entropy away from the onset of the HER.Hence,the most catalytic surface is the one with the lowest Fe coverage.
文摘Using molecular dynamics （MD） simulations, we have investigated the kinetics of the graphene edge folding process. The lower limit of the energy barrier is found to be -380 meV/A （or about 800 meV per edge atom） and -50 meV/A （or about 120 meV per edge atom） for folding the edges of intrinsic clean single-layer graphene （SLG） and double-layer graphene （DLG）, respectively. However, the edge folding barriers can be substantially reduced by imbalanced chemical adsorption, such as of H atoms, on the two sides of graphene along the edges. Our studies indicate that thermal folding is not feasible at room temperature （RT） for clean SLG and DLG edges and is feasible at high temperature only for DLG edges, whereas chemical folding （with adsorbates） of both SLG and DLG edges can be spontaneous at RT. These findings suggest that the folded edge structures of suspended graphene observed in some experiments are possibly due to the presence of adsorbates at the edges.
