CuCo Partially Alloy Nanoparticles Anchored on g-C ₃ N ₄ for Sacrificial Photocatalytic H ₂ Production and CO ₂ Reduction: Mechanistic Insights from X-ray Absorption Spectroscopy

Developing multifunctional photocatalysts with engineered interfaces is essential for efficient solar-to-chemical energy conversion and CO 2 mitigation. Herein, we report a nonnoble-metal photocatalyst consisting of CuCo bimetallic alloy nanoparticles anchored on citric-acid-functionalized graphitic carbon nitride (CGCN) via a surfactant-assisted coreduction strategy. The resulting CuCo/CGCN nanocomposite exhibited enhanced interfacial interaction, which is suggested to contribute to visible-light-driven hydrogen evolution and CO 2 reduction under mild aqueous conditions. Structural characterization confirms the uniform dispersion of CuCo alloy nanoparticles, while optical and electrochemical studies reveal enhanced visible-light absorption and improved charge separation. The nanoscale morphology and intimate interfacial contact between the ∼38 nm CuCo alloy nanoparticles and CGCN nanosheets promote efficient charge transport and enhanced surface catalytic activity. X-ray absorption spectroscopy (XAS) indicates the presence of electronic interaction between Cu and Co species along with pronounced metal–support interactions. XANES analysis suggests a possible redistribution of electron density between Cu and Co species, while EXAFS and WT-EXAFS analyses confirm heteroatomic Cu–Co bonding and metal–ligand coordination. Benefiting from these synergistic effects, the optimized 5 wt % CuCo(3:1)/CGCN catalyst achieves a visible-light-driven sacrificial photocatalytic hydrogen evolution rate of 4823.2 ± 189.9 μmol g –1 h –1 in the presence of methanol, outperforming both CuCo nanoparticles and pristine CGCN. In addition, efficient photocatalytic CO 2 reduction is achieved, producing 902 ± 28.10 μmol g –1 of products in 10 h, primarily CH 3 OH (73%) and CH 3 CH 2 OH (27%). The enhanced photocatalytic performance is attributed to nanoscale alloying effects, interfacial electronic modulation, and morphology-dependent charge separation dynamics. This work highlights a scalable, nonnoble-metal photocatalytic platform for integrated hydrogen generation and CO 2 -to-fuel conversion.