First Principles Calculations On Structure And Hydrogen Reaction Performance Of Single Atom Co Decorated-TiO₂?101?

Photocatalytic splitting of water is an important hydrogen production method.In this thesis,we use the density functional theory?DFT?+U method,as implemented in the Vienna ab initio simulation?VASP?package,to study the geometric structures,electronic energies and hydrogen evolution reaction?HER?and mechanism of single-atom Co-and Cu-doped TiO₂?101?surface,respectively.First of all,we explore the doping case of single-atom Co into the TiO₂?101?surfaces.The motivation is that Co is not only cheap and easily available,but also a classic representative of,ferromagnetic atoms such as Fe,Co,and Ni.Two types of doping modes containing atom adsorption and substitution and corresponding doping configurations are taken into account.Results show that the atom adsorption is more preferable than the atom substitution,and the most stable doping configuration is the single-atom Co on the hollow sites of surface interstice,which is consisted of 4 surface O atoms,O4c-hollow.Furthermore,we study the possible HER process and performance of Co-doped TiO₂?101?surface,and find that once the surface O atoms are fully hydroxylated by the H from the reduction of H+,the subsequent HER just occur.The doped Co atom is the only reaction site,and the associated free energies show the catalytic performance of Co-doped TiO₂ is obviously superior to that of the Co bulk.Moreover,the charge transfer and interaction between Co and TiO₂ certainly will produce some new impurity states in the gap of TiO₂,,thus enhancing the light absorption of photocatalyst,TiO₂.Next,we also study he effects of the single-atom Cu doped into TiO₂?101?surface on the HER process and performance.Similarly,the most stable and facile single-atom decorated configuration of Cu is the adsorption in which the single-atom Cu locates on the hollow sites of surface interstice,which is consisted of 4 surface O atoms,O4c-hollow-Furthermore,we find that after the two coordination O are saturated by the H atoms,the subsequent HER of Cu-doped TiO₂?101?surface just takes place.The single atom Cu is the only reaction site,Importantly,the calculated free energies of the HER show that the enhanced catalyticperformance of Cu-doped TiO₂ is much superior to the Pt?111?.Moreover,!the charge transfer and interaction between Cu and TiO₂ will produce thenew gap doped states,which result in the enhancement of light absorptionof photocatalyst substrate,TiO₂.In short,our computational study shows that the single-atom Cu dopedTiO₂?101?surface can completely replace the commercial Pt/C catalysts asthe highly-efficient and cheap electrode for HER.Our finding will provide powerful support for the exploitation of the new efficient and robust HER catalysts in photocatalytic water splitting,and further develop and improve the theory of the single-atomic catalysis.