Metallic bismuth nanoclusters confined in micropores for efficient electrocatalytic reduction of carbon dioxide with long-term stability

Electrochemical reduction of CO₂ to formate via renewable electricity is a cost-effective route. However, the existing bismuth-based electrocatalysts are in oxide form and involve in-situ reduction to metallic bismuth during CO₂ reduction. In this work, we demonstrate a nanocomposite electrocatalyst by confining Bi nanoclusters into porous carbons (Bi NCs@PC). In particular, the Bi NCs show excellent stability that can maintain zero valences during long-term electrocatalysis or after months of storage in the air. The as-synthesized Bi NCs@PC catalyst achieves up to 96 % formate Faradaic efficiency (FE) at −1.15 V versus reversible hydrogen electrode. Notably, the FE only attenuates by 7.3 % after 30 days of storage under ambient conditions. In-situ Raman spectrum identify the key intermediates during formate formation. Moreover, Bi NCs encapsulated in carbon micropores could significantly reduce the formation energy of the intermediate *OCHO by density functional theory.