Vacancy mediated Z-scheme charge transfer in a 2D/2D La₂Ti₂O₇/g-C₃N₄ nanojunction as a bifunctional photocatalyst for solar-to-energy conversion

The rational design of low-dimensional heterostructures with defects is a effective way to tackle the sophisticated challenge of harvesting solar energy to generate clean fuels such as H2 and C1 products. Herein, we designed 2D/2D La2Ti2O7/g-C3N4 nanocomposites with abundant oxygen vacancies as an efficient visible light-driven bifunctional photocatalyst for H2 evolution and CO2 reduction reactions. Through both experimental and DFT study, a defined oxygen vacancy in La2Ti2O7 was confirmed. The oxygen vacancy mediated Z-scheme mechanism verified by ESR analysis plays a significant role in the generation of clean fuels, leading to H2, CH3OH and CO generation with a much higher yield than that of defective La2Ti2O7 and g-C3N4 alone. These 2D/2D nanojunction induces a rapid electron injection from the defect sites of La2Ti2O7 nanosheets to g-C3N4 nanosheets and prolong the charge carriers' lifetime, thereby leading to high reducing power for clean fuel generation.