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

Abstract

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.