Electrodeposition of Bismuth Nanoplatelets from a Ph Neutral Solution on Acid-Sensitive Supports for Co2 Electrocatalytic Reduction to Formate

Bismuth is an efficient catalyst for electrochemical reduction of carbon dioxide to formate, a potential renewable energy storage media. High current densities and conversion yields are needed to scale up the electrochemical reduction of carbon dioxide, which requires high surface area catalyst supports. However, the Bi3+ ions are only soluble in aqueous solutions at low pH values (< 2), while various promising catalyst supports are acid-sensitive. Here, a way for depositing metallic Bi from a pH-neutral solution is presented. Monometallic and bimetallic thiolate-based precursors of Bi were utilized in dimethylformamide (DMF)-based deposition bath for potentiostatic electrodeposition. Bi nanoplatelets morphology was obtained with both precursors, but when a bimetallic precursor was used, thinner platelets were obtained than when a monometallic precursor was used. While high selectivity for reduction of carbon dioxide to formate (faradaic efficiency ~95%) was obtained regardless of the precursor used, the thinner platelets deposited from the bimetallic precursor resulted in ~120 mV lower overpotential. Finally, the nanoplatelets morphology was preserved when Bi was deposited on graphene foam supports, a promising—yet, acid-sensitive—high-surface-area electrode. Low onset potential (~350 mV vs. RHE) was attained with Bi-coated graphene foam, showing the prospects of this deposition approach for producing efficient electrocatalysts.