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.