A Z-scheme inorganic intergrowth bulk heterojunction to achieve photostimulated oxygen vacancy regeneration for photocatalytic CO2 reduction†

An inorganic intergrowth bulk heterojunction (IIBH) NiO(Ti)/Ti₃O₅(Ni,Ga) has been constructed by a two-stage topological pyrolysis method based on the structure memory effect of NiTiGa-LDHs. The Z-scheme mechanism for regenerating oxygen vacancies was investigated by ISI-XPS. It can be speculated that the photogenerated electron transfer process between the Ni²⁺/Ni³⁺ and Ti⁴⁺/Ti³⁺ redox pairs across the interface of the IIBH resulted in excess oxygen vacancies, which were active in the photocatalytic CO₂ reduction. This IIBH exhibited well-established photocatalytic efficiency for CO₂ reduction with CO yields up to 2560.1 μmol g⁻¹ h⁻¹, which were 6.97 times higher than those of NiTiGa-LDHs and 4.95 times higher than those of NiTiGa-MMO, respectively. In the 60 h cyclic photocatalytic CO₂ reduction experiment, the stability could still be maintained at 96.7%. This work provided an innovative approach for designing defective catalysts by electron transfer from redox pairs thus inducing the regeneration of oxygen vacancies.