Construction of ternary heterojunction photocatalyst Cu₂Cl(OH)₃/In/In₂O₃ for boosted photocatalytic CO₂ reduction performance

The photocatalytic conversion of CO₂ and H₂O into useful chemicals or fuels over semiconductor photocatalysts is regarded as a promising technology to address the problems of global warming and energy exhaustion. However, inefficient photo-absorption and slow charge dynamics limit the CO₂ photoreduction efficiency. Here, a ternary heterojunction photocatalyst, Cu₂Cl(OH)₃/In/In₂O₃ (Cu H IO), with an intimate interface is obtained <i>via</i> a hydrogen chemical reduction approach followed by hydrolysis reaction, where In species can be produced on the surface of In₂O₃ from the hydrogen chemical reaction with a calcining temperature of over 500 °C. Cu H IO exhibits enhanced photocatalytic activity for CO₂ conversion compared to pristine In₂O₃, In₂O₃ with In species (H IO), and Cu₂Cl(OH)₃/In₂O₃ (Cu IO). In the absence of sacrificial agent or cocatalyst, the yield rates of CO and CH₄ over Cu H IO are 4.36 and 1.09 μmol g^-1 h^-1, which are 8.38-fold and 18-fold that of pristine In₂O₃ (0.52 and 0.06 μmol g^-1 h^-1), respectively. The photocatalytic performance enhancement of Cu H IO results from the construction of the ternary heterojunction, with synchronous improvement in the photoresponse and charge separation of In₂O₃. Moreover, the possible CO₂ reduction pathway over Cu H IO has also been investigated and proposed. This work provides an important strategy for developing a high-efficiency heterojunction photocatalyst system for solar fuel generation.