Cyclic voltammetry driven Bi–Ag single-atom alloy electrocatalysts for enhanced CO2-to-formate conversion

Abstract

Single-atom alloy (SAA) catalysts offer synergistic electronic interactions, optimized adsorption environments, and maximized atomic utilization. Here, we report an electrochemical strategy to synthesize Bi single atoms dispersed on Ag (Bi–Ag SAAs), which serve as a promising catalyst platform for CO₂-to-formate conversion. HAADF-STEM/EDS, XPS, and XRD collectively demonstrate that cyclic voltammetry treatment reconstructs a thermally evaporated Bi layer on Ag nanoparticles supported on a carbon electrode into atomically dispersed Bi sites on Ag. The resulting Bi–Ag SAAs catalyst derived from a 15 nm Bi layer exhibited 1.9-fold higher formate faradaic efficiency and 3.5-fold higher formate selectivity than non-CV-treated samples, despite a substantially lower Bi loading. Electrochemical impedance spectroscopy reveals a charge-transfer-resistance hierarchy of Bi > AgBi > CV-AgBi under both N₂ and CO₂ saturated conditions, indicating enhanced interfacial charge transfer for CO₂ reduction at atomically dispersed Bi sites. This work provides key insight into how CV-driven reconstruction can be leveraged to create atomically dispersed single-atom alloys for advanced CO₂-reduction catalyst design.