Electrochemically deposited Sn catalysts with dense tips on a gas diffusion electrode for electrochemical CO₂ reduction

The electrochemical CO₂ reduction reaction (CO₂RR) has undergone great advances recently. The gas diffusion electrode (GDE) has been introduced to enhance productivity. However, the studies on catalysts on the GDE are scarce, especially for the production of liquid products. Here, we deposited Sn electrocatalysts electrochemically with dense tips (SnDT) on a gas permeable carbon cloth electrode. The prepared cathode had a uniform surface covered with SnDT catalysts. We achieved a high specific production rate of the CO₂RR towards formate, 1 mmol m^-2 s^-1, at only -0.76 V_RHE where partial current density and faradaic efficiency toward formate were -18.7 mA cm^-2 and 62.5%, respectively, in neutral electrolyte. Formate productivity of 65 mg h^-1 was achieved using a customized cell with 4 cm² of the SnDT GDE. Formate was stably produced for 72 h without changes in faradaic efficiency and current density. The product distribution was affected by local pH. The effect of catalyst shape was also investigated by comparing with commercial Sn nanoparticles deposited on a carbon cloth electrode.