Durable and Efficient Solar CO ₂ ‐to‐CO Conversion Enabled by Single‐Atom Ag on Zn ₃ (PO ₄ ) ₂ Cathode Coupled With a GaAs/Pt _SA @NiOOH Photoanode

Abstract The increasing necessity to reduce human‐caused carbon dioxide (CO ₂ ) emissions and shift to renewable fuels underscores the significance of innovative carbon‐conversion methods, with photoanode‐assisted CO ₂ reduction (photoanode‐CO2RR) recently emerging as a promising strategy. This study introduces a novel interface‐engineered catalyst—Ag _SA @Zn ₃ (PO ₄ ) ₂ –comprising isolated Ag single atoms (SAs) are uniformly doped onto zinc phosphate(Zn ₃ (PO ₄ ) ₂ ) nanocubes, promoting efficient charge transfer and delivering highly selective CO production in CO ₂ RR. Density functional theory (DFT) calculations further demonstrate that the doping of Ag SAs alters the electronic structure of Zn ₃ (PO ₄ ) ₂ , optimizing the adsorption of reaction intermediates. A photoelectrochemcial (PEC) flow‐cell integrating a GaAs/Pt _SA @NiOOH photoanode and an Ag _SA @Zn ₃ (PO ₄ ) ₂ cathode achieve carbon monoxide (CO) production with a solar‐to‐fuel efficiency (STF) of 4.7% and a Faradaic efficiency (FE) of 94%, demonstrating significantly improved CO ₂ reduction kinetics. Moreover, the integrated Ag _SA @Zn ₃ (PO ₄ ) ₂ ||Pt _SA @NiOOH standalone photo‐assisted system, powered by a photovoltaic (PV) module, operate continuously under zero external bias, achieving an average CO FE _CO of 90%. This outstanding performance corresponds to a solar‐to‐CO conversion efficiency (ηSTF _co ) of 8.8% under AM 1.5G illumination, showcasing its potential as an effective and durable solution for CO ₂ reduction.