Trace Alloying Unleashed: AuPt Nanoalloys Strategy Preserves Plasmonic Properties on Au Nanobipyramids While Boosting Electron Transfer for Visible Light Ammonia Synthesis

ABSTRACT Photocatalysis, leveraging the redox capabilities of photocatalysts under light irradiation, emerges as a promising approach for clean energy conversion and pollution control. In this study, we engineered Au nanobipyramids (Au NBPs) with trace amounts of AuPt alloy to enhance their photocatalytic efficiency for selective ammonia synthesis. By modulating the reduction kinetics and precursor ratios, we synthesized three distinct Pt configurations: dense Pt layers (Au NBPs@Pt d ), sparse Pt clusters (Au NBPs@Pt s ), and trace AuPt alloy (Au NBPs@Au/Pt alloy ). Among them, Au NBPs@Au/Pt alloy exhibited superior performance in photoelectrocatalytic nitrite‐to‐ammonia conversion, achieving a 10‐fold increase in ammonia production compared to Au NBPs and a 1.26‐fold enhancement under illumination vs. dark conditions. Multimodal characterization revealed that the ultra‐low AuPt alloy loading preserved the intrinsic localized surface plasmon resonance (LSPR) properties of Au NBPs while enhancing hot carrier generation and interfacial electron transfer efficiency. Density functional theory (DFT) calculations further confirmed that AuPt alloying optimized reaction free energy profiles by reducing adsorption barriers for key intermediates. This work not only advances the rational design of plasmonic catalysts but also demonstrates the potential of trace metal alloying for achieving high selectivity in visible‐light‐driven catalytic reactions, holding significant implications for sustainable energy conversion.