Conductive MOF/defect titanium dioxide S-scheme heterojunction with enhanced charge transfer for efficient photocatalytic hydrogen generation

Developing of advanced heterojunction photocatalysts with high electron-hole separation efficiency and matching band locations is critical for photocatalytic hydrogen production. Herein, a novel S-scheme heterojunction Ni₃(HITP)₂/Ti_1-xO₂ combined titanium vacancy titanium dioxide (Ti_1-xO₂) with 2D conductive MOF Ni₃(HITP)₂ can address this challenge. Ti_1-xO₂, whose band gap value is 0.35 eV smaller than that of TiO₂, introduces shallow acceptor levels to make the material appear as a P-type semiconductor. SPV tests, in-situ XPS, active species capture experiments, and band structure characterization proved the existence of S-scheme heterojunction, which greatly promoted the compound of ineffective photoexcited carriers. The H₂ generation rate of 4 wt% Ni₃(HITP)₂/Ti_1-xO₂-2 under solar light is 3.52 mmol/h/g, which is 8.2 times and 2.5 times of TiO₂ and Ti_1-xO₂. This study offers a consult for the devise of conductive MOF-based S-scheme heterojunction photocatalyst for H₂ production.