Enhanced photocatalytic CO2 reduction activity on the novel Z-scheme Co-MOF/Bi2MoO6 to form CO and CH4

Abstract

Herein, a novel Z-scheme Co-MOF/Bi₂MoO₆ was synthesized by in-situ growth method. The photocatalytic CO₂ reduction effect of Co-MOF/Bi₂MoO₆ was significantly improved, and the formation rates of CO and CH₄ reached 19.76 and 8.24 μmol·g⁻¹·h⁻¹, which corresponded to 1.61 and 2.38 times of Co-MOF (CO: 12.31 μmol·g⁻¹·h⁻¹) and Bi₂MoO₆ (CH₄: 3.46 μmol·g⁻¹·h⁻¹), respectively. The increased photocatalytic activity of Co-MOF/Bi₂MoO₆ resulted from the enhanced visible light capture capability and the Z-scheme heterojunction formed among Co-MOF and Bi₂MoO₆, which promoted the efficient separation of photogenerated carriers while retaining the highest redox capacity. The Z-scheme charge transfer direction of Co-MOF/Bi₂MoO₆ was confirmed by DRS, XPS, ESR, UPS, and the photocatalytic reaction mechanism was explained. In addition, the active substances and intermediates of Co-MOF/Bi₂MoO₆ in the photocatalytic CO₂ reduction process were investigated using ESR and in-situ FT-IR. The work offers a idea for building MOFs-based heterojunctions to improve the effect of photocatalytic CO₂ reduction.