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Facile synthesis of efficient electrocatalysts that can selectively convert CO2 into value-added chemicals remains a challenge. This study presents the electrochemical synthesis of porous Bi dendrite electrodes and details on their activity toward CO2 conversion to formate in aqueous bicarbonate solutions. The as-synthesized multi-layered porous dendrite Bi electrodes exhibit the faradaic efficiency (FE) of ~100% of formate production. The added halides and cations significantly influence the steady-state partial current density for formate production (J FM) (Cl- > Br- ~ I-; Cs+ > K+ > Li+). Density functional theory calculations have revealed that the reaction pathway involving the species *OCOH occurs predominantly, while co-existence of Cs+ and Cl- changes the overall reactions more spontaneously. A photovoltaic cell-assisted electrocatalysis produces formate with FEs of ~95% (J FM ~10 mA cm-2) at an overall solar conversion efficiency of ~8.5%. The Bi electrodes maintain their activity over 360 h without a change in the surface states. Figure 1