Modification of Anatase TiO₂ with Amorphous Cu Nanoparticles: An Efficient Photocatalyst for the Reduction of CO₂ to CO/CH₄

Titanium dioxide-based photocatalysts have garnered significant attention for CO₂ reduction reactions (CO₂RR) toward fuel production, with noble metal incorporation markedly enhancing photocatalytic efficiency. However, the development of cost-effective alternatives to expensive metals (e.g., Au, Ag) remains a critical challenge. Herein, amorphous copper nanoparticles (a-Cu NPs) were successfully anchored onto anatase TiO₂ via a chemical reduction method using Cu(NO₃)₂·3H₂O as the precursor. The optimized 4 wt % a-Cu/TiO₂ catalyst (4CT) demonstrated remarkable activity, achieving methane and CO production rates of 3.0 and 18.4 μmol·g^-1·h^-1, respectively, corresponding to 10.0-fold and 7.3-fold enhancements over pristine TiO₂. CO₂-TPD revealed that the high surface disorder of a-Cu NPs significantly strengthened CO₂ chemisorption. In situ Fourier transform infrared spectroscopy (FTIR) further indicated that a-Cu loading enabled preferential CO₂ adsorption over H₂O on TiO₂ surfaces while accelerating the formation of the key intermediate *COOH. This work proposes a synergistic strategy integrating nonprecious metal modification with interfacial engineering, offering a cost-effective pathway to develop high-performance photocatalysts for sustainable CO₂ conversion.