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

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 JFM (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 % (JFM ≈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.