Ion-Enhanced Conversion of CO₂ into Formate on Porous Dendritic Bismuth Electrodes with High Efficiency and...

Facile synthesis of efficient electrocatalysts that can selectively convert CO₂ to value-added chemicals remains a challenge. Herein, the electrochemical synthesis of porous Bi dendrite electrodes and details of their activity toward CO₂ conversion to formate in aqueous solutions of bicarbonate are presented. The as-synthesized multilayered, porous, dendritic Bi electrodes exhibit a faradaic efficiency (FE) of approximately 100 % for formate production. Added halides and cations significantly influence the steady-state partial current density for formate production J_FM (Cl^- >Br^- ≈I^- ; Cs⁺ >K⁺ >Li⁺ ). DFT calculations revealed that the reaction pathway involving the species *OCOH occurs predominantly and the presence of both Cs⁺ and Cl^- makes the overall reaction more spontaneous. Photovoltaic-cell-assisted electrocatalysis produced formate with an FE of approximately 95 % (J_FM ≈10 mA cm^-2 ) at an overall solar conversion efficiency of approximately 8.5 %. The Bi electrodes maintain their activity for 360 h without a change in the surface states.