Structurally Ordered NiCu Alloy With Dynamically Regenerating Active Sites Enables Efficient Photocatalytic CO₂...

Photocatalytic conversion of CO₂ to CH₄ is a promising pathway for carbon utilization, but the reaction is hindered by complex multi-electron transfer steps and sluggish intermediate transformation kinetics. In this study, we synthesize a series of NiCu bimetallic catalysts (NiCu/ZrO₂) featuring distinct compositional structures, namely ordered, disordered, and phase-separated (PhaseSep), to systematically elucidate how the spatial arrangement of Ni and Cu influences catalytic behavior. We further investigate how the dynamic evolution of active sites under reaction conditions governs photocatalytic CO₂ methanation. Among the catalysts, NiCu/ZrO₂(Ordered) exhibits the highest CH₄ formation rate of 559.9 µmol g^-1 h^-1, which is markedly higher than that of NiCu/ZrO₂(Disordered) and NiCu/ZrO₂(PhaseSep), demonstrating that the atomic-level organization of the bimetallic phase plays a decisive role in photocatalytic performance. In situ XPS and DRIFTS analyses reveal that Ni⁰, Cu⁰, and surface defective oxygen (O_def) sites undergo rapid and reversible regeneration during the reaction, enabling more efficient activation and transformation of key reaction intermediates. This dynamic renewal of active sites is identified as the origin of the superior activity of NiCu/ZrO₂(Ordered). These findings show that tailoring bimetallic site geometry is an effective strategy for enhancing photocatalytic CO₂ methanation.