Construction of Co1‐xZnxFe2xGa2–2xO₄ (0<x≤0.6) Solid Solutions for Improving Solar Fuels Production in Photocatalytic CO₂ Reduction by H₂O Vapour

Solid solutions are garnering substantial attention in the realm of solar energy utilization due to their tunable electronic properties, encompassing band edge positions and charge‐carrier mobilities. In this study, we designed and synthesized Co 1‐x Zn x Fe 2x Ga 2–2x O 4 (0<x≤0.6) as a photocatalyst for CO 2 conversion using H 2 O. Careful optical and photo/electrochemical characterizations unveiled that the relative content of CoGa 2 O 4 and ZnFe 2 O 4 not only substantially influences light absorption in the full solar spectrum but also modulates valence and conduction band positions. We thoroughly assessed the photocatalytic activity of Co 1‐x Zn x Fe 2x Ga 2–2x O 4 and found that when x=0.35, the solid‐solution catalyst achieved a remarkable CO 2 reduction rate to CH 4 and CO (31.5 μmol g −1 h −1 ). Furthermore, this optimized solid‐solution catalyst demonstrated impressive photostability. Characterization and DFT calculations revealed that the formation of a solid solution not only reduces the band gap and promotes the separation of electron‐hole pairs to accelerate efficient CO 2 photoreduction, but also the introduction of more FeO 6 octahedral active sites in Co 1‐x Zn x Fe 2x Ga 2–2x O 4 solid solutions enhanced the effective photoreduction of CO 2 . This design results in high conversion efficiencies for producing solar fuels through CO 2 reduction with H 2 O.