Theoretical Studies On The Highly Efficient HER Catalysts With Embedding The Tetrahedral 3d Transition Metal TM₄ Clusters Into Graphdiyne And The Relevant Mechanisms

Currently,the depletion and combustion of fossil energy bring more and more environmental problems,and people’s demand for energy is getting less and less satisfied.Thus,the development and utilization of new energy is becoming a hot spot,attracting the interest of scientists.As a green and pollution-free new energy,hydrogen energy has gradually entered people’s vision.Hydrogen energy is a kind of molecular fuel with high density,recyclable and pollution-free by-products.Electrochemical water splitting can be considered as one of the most promising and practical approaches to produce hydrogen.The hydrogen evolution reaction（HER）is a half reaction（2H⁺+2e^-=H₂）in water splitting process.The appropriate catalyst is needed to reduce the reaction overpotential.As everyone knows,precious metal Pt is the most effective HER catalyst,but it can not be used in the mass production,due to its high price and low abundance.Thus,theoretical design and exploration of new HER catalyst based on inexpensive metal has become more and more important.Recently,the research on HER catalyst based on two-dimensional materials is more and more popular,in view of the fact that two-dimensional materials have a unique atomic thickness plane structure,and can expose more active sites due to the large surface area.On the basis of the density functional theory（DFT）calculations,we have systematically investigated the structures and hydrogen evolution reaction（HER）catalytic activities for a series of new composite systems TM₄@GDY（TM=Sc,Ti,Mn,Fe,Co,Ni and Cu）,which are constructed by embedding the tetrahedral3d transition metal TM₄ clusters in the in-plane cavity of two-dimensional（2D）π-conjugated graphdiyne（GDY）.The computed results reveal that compared with the constituent subunits,namely the sole TM₄ cluster and GDY,all these composite TM₄@GDY nanostructures can uniformly exhibit the considerably high HER catalytic activity over a wide range of hydrogen coverage,and especially Fe₄@GDY and Co₄@GDY systems can possess higher HER activity.The high HER catalytic activity for TM₄@GDY can be mainly due to the occurrence of obvious electron transfer from the TM₄ cluster to GDY,significantly activating the correlative C and TM atoms.In addition,the results show that all these composite TM₄@GDY systems can also exhibit high structural stability and good conductivity.Therefore,all of them can be considered as a new kind of promising HER catalysts,and this study can provide new strategies for designing low-cost and high-performance 2D carbon-based electrocatalysts.