Synergistic Effect of Cu Single Atoms and Au–Cu Alloy Nanoparticles on TiO2 for Efficient CO2 Photoreduction

The synergy between metal alloy nanoparticles (NPs) and single atoms (SAs) should maximize the catalytic activity. However, there are no relevant reports on photocatalytic CO₂ reduction via utilizing the synergy between SAs and alloy NPs. Herein, we developed a facile photodeposition method to coload the Cu SAs and Au-Cu alloy NPs on TiO₂ for the photocatalytic synthesis of solar fuels with CO₂ and H₂O. The optimized photocatalyst achieved record-high performance with formation rates of 3578.9 for CH₄ and 369.8 μmol g^-1 h^-1 for C₂H₄, making it significantly more realistic to implement sunlight-driven synthesis of value-added solar fuels. The combined in situ FT-IR spectra and DFT calculations revealed the molecular mechanisms of photocatalytic CO₂ reduction and C-C coupling to form C₂H₄. We proposed that the synergistic function of Cu SAs and Au-Cu alloy NPs could enhance the adsorption activation of CO₂ and H₂O and lower the overall activation energy barrier (including the rate-determining step) for the CH₄ and C₂H₄ formation. These factors all enable highly efficient and stable production of solar fuels of CH₄ and C₂H₄. The concept of synergistic SAs and metal alloys cocatalysts can be extended to other systems, thus contributing to the development of more effective cocatalysts.