Self-Supporting Bi–Sb Bimetallic Nanoleaf for Electrochemical Synthesis of Formate by Highly Selective CO₂ Reduction

Abstract

Electrocatalytic reduction of CO₂ into valuable fuels and chemical feedstocks in a sustainable and environmentally friendly manner is an ideal way to mitigate climate change and environmental problems. Here, we fabricated a series of self-supporting Bi-Sb bimetallic nanoleaves on carbon paper (CP) by a facile electrodeposition method. The synergistic effect of Bi and Sb components and the change of the electronic structure lead to high formate selectivity and excellent stability in the electrochemical CO₂ reduction reaction (CO₂RR). Specifically, the Bi-Sb/CP bimetallic electrode achieved a high Faradic efficiency (FE_formate, 88.30%) at -0.9 V (vs RHE). The FE of formate remained above 80% in a broad potential range of -0.9 to -1.3 V (vs RHE), while FE_CO was suppressed below 6%. Density functional theory calculations showed that Bi(012)-Sb reduced the adsorption energy of the *OCHO intermediate and promoted the mass transfer of charges. The optimally adsorbed *OCHO intermediate promoted formate production while inhibiting the CO product pathway, thereby enhancing the selectivity to formate synthesis. Moreover, the CO₂RR performance was also investigated in a flow-cell system to evaluate its potential for industrial applications. The bimetallic Bi-Sb catalyst can maintain a steady current density of 160 mA/cm² at -1.2 V (vs RHE) for 25 h continuous electrolysis. Such excellent stability for formate generation in flow cells has rarely been reported in previous studies. This work offers new insights into the development of bimetallic self-supporting electrodes for CO₂ reduction.