Construction of Co_1‐xZn_xFe_2xGa_2–2xO₄ (0<x≤0.6) Solid Solutions for Improving Solar Fuels Production in Photocatalytic CO₂ Reduction by H₂O Vapour

Abstract

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 Co1‐xZnxFe2xGa2‐2xO4 (0&lt;x≤0.6) as a photocatalyst for CO2 conversion using H2O. Careful optical and photo/electrochemical characterizations unveiled that the relative content of CoGa2O4 and ZnFe2O4 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 Co1‐xZnxFe2xGa2‐2xO4 and found that when x=0.35, the solid‐solution catalyst achieved a remarkable CO2 reduction rate to CH4 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 CO2 photoreduction, but also the introduction of more FeO6 octahedral active sites in Co1‐xZnxFe2xGa2‐2xO4 solid solutions enhanced the effective photoreduction of CO2. This design results in high conversion efficiencies for producing solar fuels through CO2 reduction with H2O.