Promoting photocatalytic CO2 reduction to CH4 via a combined strategy of defects and tunable hydroxyl radicals

A well-designed photocatalyst with excellent activity and selectivity is crucial for photocatalytic CO₂ conversion and utilization. TiO₂ is one of the most promising photocatalysts. However, its excessive surface oxidation potential and insufficient surface active sites inhibit its activity and photocatalytic CO₂ reduction selectivity. In this work, highly dispersed Bi₂Ti₂O₇ was introduced into defective TiO₂ to adjust its oxidation potential and the generation of radicals, further inhibiting reverse reactions during the photocatalytic conversion of CO₂. Moreover, an in situ topochemical reaction etching route was designed, which achieved defective surfaces, a contacted heterophase interface, and an efficient electron transfer path. The optimized heterophase photocatalyst exhibited 93.9% CH₄ selectivity at a photocatalytic rate of 6.8 μmol·g⁻¹·h⁻¹, which was 7.9 times higher than that of P25. This work proposes a feasible approach to fabricating photocatalysts with well-designed band structures, highly dispersed heterophase interfaces, and sufficient surface active sites to effectively modulate the selectivity and activity of CO₂ photoreduction by manipulating the reaction pathways.