Ion‐Enhanced Conversion of CO 2 into Formate on Porous Dendritic Bismuth Electrodes with High Efficiency and Durability

Facile synthesis of efficient electrocatalysts that can selectively convert CO 2 to value‐added chemicals remains a challenge. Herein, the electrochemical synthesis of porous Bi dendrite electrodes and details of their activity toward CO 2 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.