A Theoretical Study For Electrocatalytic Hydrogen Evolution Reaction Of Molybdenum Sulfide Compounds

Water electrolysis is a commonly used technique to produce hydrogen.Combined with renewable energy can significantly reduce the cost of hydrogen production.Transition metal sulfides are found as noble metal-free and efficient catalysts towards HER.But there remain disagreements for its real active sites,and the roles of the substrates have not been clear.It is of great significance to study the real active sites and the effects of the substrates on the design of catalysts in the future.We determine the reaction pathways,barriers and the role of carriers by Density Functional Theory(M06L)calculations.The main work and innovation are summarized as follows:(1)Based on two Molybdenum sulphur HER catalysts:[M03S13]2-and[Mo3S7Cl6]2-we study the reation paths by Density Functional Theory(M06L)calculations compared with B3LYP and ωB97XD.First,we investigate the adsoption of hydrogrn on all sites of the two catalysts.It is found that the protonated[Mo3S13]2-cluster is more favorable towards adsorption of hydrogen.This indicates that △GH is not an accurate descriptor for HER when considering the absorption of one molecular hydrogen.In addition,the mechanisms take place through the Volmer-Heyrovshy mechanisms for two catalysts involving a bridging sulphur hrdride and a hydronium cation.(2)Then we consider the effects of substrates by coupling the two calatysts with conductive carbon species.For two calatysts,their adsorption capacities towards hydrogen are enhanced and the hydrides become more stable when they are coupled with carbon substrates.So we believe the conductive carbon substrates work for stabiling hydride intermediates.The mechanisms take place through the Volmer-Heyrovshy mechanisms for two catalysts involving a bridging sulphur hrdride and a hydronium cation,which is consistentwith the experimental Tafel slope.