In situ construction of a 2D CoTiO3/g-C3N4 photocatalyst with an S-scheme heterojunction and its excellent performance for CO2 reduction

Abstract

To address the high combination rate and low reductive oxidation capacity of photogenerated electron–hole pairs in photocatalysts, the synthesis of S-scheme heterojunction photocatalysts is considered as an effective strategy to improve the photocatalytic performance. In this work, 2D CoTiO₃/g-C₃N₄(CTO/CN) photocatalysts with an S-scheme heterojunction were prepared by in situ growth of CoTiO₃ nanoparticles onto 2D porous g-C₃N₄ nanosheets. Compared with the pure g-C₃N₄, CTO/CN catalysts with different CTO contents exhibit excellent photocatalytic CO₂ reduction performance under visible light illumination. The unique band alignment of S-scheme heterojunctions not only suppresses the recombination of photogenerated electron–hole pairs but also produces a sufficient photovoltage to drive the CO₂ reduction reaction. Among them, the 2.0% CTO/CN sample exhibits the best photocatalytic activity for CO₂ reduction to CO (at a rate of 236.2 μmol g⁻¹ h⁻¹) and H₂ (at a rate of 75.2 μmol g⁻¹ h⁻)¹ which were 229.3 and 221.2 times higher than those of pure g-C₃N₄. Meanwhile, the 2.0% CTO/CN sample exhibits excellent photocatalytic stability during the photocatalytic CO₂ reduction cycle reaction. This work provides a new insight into the design of S-scheme heterojunction photocatalysts for photocatalytic CO₂ reduction.