Mechanism upon Conversion of Syngas Catalyzed by Single Atom Mo Supported on Graphene:Role of Carbon Component and Impact from Mo-C Interactions
The catalytic behaviors of metal for syngas conversion are related to the carbonization of the metal,however,the formed metallic carbides are of complicated composition and structures,making the identification of the active phase of the catalysts be challengeable,so it is significant to investigate the role of the carbon component of the catalysts.In this work,we studied computationally mechanisms of syngas conversion to alcohols on single atom Mo supported on pristine graphene(Mo/pri-graphene)and single-carbon vacant graphene(Mo/sv-graphene)by means of density functional theory(DFT)method to explore the regulated effect of carbon component on C—O activation.The results show that it is significantly different for mechanisms of syngas conversion on Mo/pri-graphene with weak Mo-C interactions and Mo/sv-graphene with strong Mo-C interactions.On Mo/pri-graphene the preferred pathway is CO→HCO→CH2O→CH3O→CH3/CH4,and species CH3O is of some stability due to high activation free energy of its further transformation into CH3/CH4,while on Mo/sv-graphene the preferred pathway is CO→HCO→CH2O→CH2OH→CH3OH/CH3(CH4),and the coexistence of species CH3OH and CH3(CH4)provides a possibility for the following carbon chain propagation.The activation free energy of the elementary steps of CO hydrogenation on Mo/sv-graphene is generally lower than that on Mo/pri-graphene.The reasons are the lower interactions between Mo/sv-graphene and the substrate,and the participation of the carbon component of Mo/sv-graphene during the activation/transformation of the substrate.Thus,the carbon component of catalysts can regulate(and/or take participate in)the interaction of the catalysts with the substrates,and then make an improvement on the activity and selectivity.
Single atomMo/grapheneSyngas conversionCarbonMechanism
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