Photocatalytic Her Performance Of TiO₂-supported Single Atom:Catalyst Based On Electronic Regulation:A DFT Study

Hydrogen is a kind of sustainable clean energy.Sunlight driven hydrogen evolution reaction（HER）from water splitting assisted by catalysts is very crucial for developing clean energy technologies.Single atom catalysts such as atomically dispersed Pt on anatase（Pt₁/TiO₂）have exhibited the excellent photocatalytic HERactivity,however,the role of single atom in photocatalytic hydrogen evolution andimpacts of photocatalytic performance are still unknown.Based on electronic regulation,the mechanism and impacts of photocatalytic HER of TiO₂-supported noble metal single atom catalysts have been studied,which provided theoretical guidance for improving the photocatalytic HER performance.The photoexcitation and electron migration on Pt₁/TiO₂（101）surface have been studied to explore the effect of single atom Pt.Supporting single atom Pt could narrow the band gap of TiO₂,enchance the optical absorption properties.After single atom Pt loaded,TiO₂surface lattice relaxes,the d-band center of surface Ti atoms reduce,which are beneficial to the excited electrons localization and transfer from bulk to surface.The effect of excited electrons on each step of water splitting and hydrogen evolution on Pt₁/TiO₂（101）surface is explored.Excited electrons could not participate in the process of O-H cleavage,but can participate in the process of proton reduction and greatly reduce the hydrogen evolution energy.Therefore,the hydrogen evolution energy can be used as an index to evaluate the activity of TiO₂-supported single atom catalysts.The photocatalytic hydrogen evolution energy of M₁/TiO₂(（M=Pd,Pt,Rh,Ir）were calculated and factors affecting the photocatalytic performance of single atom catalysts were studied.The activity of hydrogen evolution is related to the number of d-band electrons of single noble atom.The number of valence electrons of single atom Pd and Pt are 10,thus they will not receive the excited electrons and require less energy for hydrogen evolution.The number of valence electrons of single atom Rh and Ir are 9,thus they will receive one excited electron and require more energy for hydrogen evolution.By regulating the number of d electrons of the noble metal atom,this paper comfirm that the increase of the number of d electrons in the single atom could reduce the hydrogen evolution energy and thus promote the hydrogen evolution process.