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.