Structural, electronic, optical and photocatalytic properties of KTaO₃ with NiO cocatalyst modification

KTaO₃ loaded with NiO cocatalyst is an efficient photocatalyst that has been widely applied to various photocatalytic reactions. In this work, density functional theory calculations have been utilized to investigate the interfacial geometries, electronic structures, charge transfer, optical absorption, and water oxidation mechanism of the NiO(001)/KTaO₃(001) slab model. The formation of O-Ni and Ta-O interfacial bonds is thermodynamically stable, indicating a covalent interaction between the two components of the heterostructure. The calculated density of states using the PBE+U and HSE06 methods shows that in the NiO/KTaO₃ heterostructure, the valence band maximum and conduction band minimum of NiO are located above those of KTaO₃, indicating the formation of type-II band alignment. Upon light irradiation, the photogenerated electrons accumulate at the KTaO₃ side and photogenerated holes gather at the NiO side. The difference in electrostatic potentials around the interface as a driving force boosts the migration of electrons and holes to different domains of the interface, which is beneficial to extending the lifetime of photoinduced carriers and improving the photocatalytic activity of the KTaO₃ system. The formation of an interface between NiO and KTaO₃ evidently reduces the overpotential of the oxygen evolution reaction because the adsorption of intermediates in the water oxidation process becomes more moderate. Our results provide new insights into understanding the influence of loading NiO cocatalyst on the photocatalytic performance of KTaO₃, which provides a theoretical guidance for designing new semiconductor-based photocatalysts.