Photocatalytic H2 evolution over CuCoSe2 nanoparticles decorated TiO2 nanosheets with S-scheme charge separation route

The construction of S-scheme heterojunctions via exploring semiconductors with suitable energy band structures can effectively improve the photocatalytic performance of TiO₂. In this work, CuCoSe₂/TiO₂ heterojunction were prepared using solvent evaporation strategy by their different surface charge properties. The investigation indicates that rates of H₂ evolution (rH₂) of the system increases significantly from 138.1 (TiO₂) to 3773.8 μmol·g⁻¹·h⁻¹ (CuCoSe₂/TiO₂). It is found that the incorporation of CuCoSe₂ can extend the visible light absorption range of the system, increase the electrochemically active surface area, facilitate charge generation and decrease the transfer resistance, reduce the H₂ production overpotential and the water contact angle. Further investigation reveals that a bimetallic selenide CuCoSe₂ exhibit superior enhancement activity compared to their monometallic selenides (CuSe₂, CoSe₂) due to the synergistic effect of Co and Cu. Especially, the charge transfer between CuCoSe₂ and TiO₂ follows S-scheme charge separation route, which can effectively enhance charge separation/migration, reserve e⁻ with strong reducing ability in TiO₂, thereby promoting the H₂ evolution kinetics. Moreover, the heterojunction also demonstrates exceptional stability throughout the cycle experiment. The present work establishes an experimental basis for the advancement of highly efficient and stable bimetallic selenides related heterojunctions in the field of photocatalytic H₂ evolution.