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.