Bi₃O₄Cl/g‑C₃N₄/Cd_0.5Zn_0.5S Double Z‑Scheme Heterojunction Photocatalyst for Highly Selective CO₂ Reduction to Methane

Solar-energy-driven CO₂ hydrogenation is a promising strategy to alleviate the climate crisis. Methane is a desirable derivative of CO₂ reduction. However, developing a photocatalyst for highly active and selective CH₄ generation remains challenging. Herein, we report a double Z-scheme Bi₃O₄Cl/g-C₃N₄/Cd_0.5Zn_0.5S photocatalyst for efficient reduction of CO₂ to CH₄. In situ characterization techniques confirmed that the charge migration mechanism in Bi₃O₄Cl/g-C₃N₄/Cd_0.5Zn_0.5S promotes charge separation through double internal electric fields. As a result, the optimized C0.01B0.02C catalyst displayed a formation rate high up to 25.34 μmol g^–1 h^–1 and a selectivity of 96.52% of CH₄. Moreover, the AQY of CO₂ conversion on C0.01B0.02C (1.84%) was almost 41 times higher than that of the bare CN. This study provides a novel perspective to develop heterojunction photocatalysts for selective CO₂ conversion to CH₄.