Promoting electrocatalytic CO(2) reduction to formate via sulfur-boosting water activation on indium surfaces

Electrocatalytic reduction of CO(2) to fuels and chemicals is one of the most attractive routes for CO(2) utilization. Current catalysts suffer from low faradaic efficiency of a CO(2)-reduction product at high current density (or reaction rate). Here, we report that a sulfur-doped indium catalyst exhibits high faradaic efficiency of formate (>85%) in a broad range of current density (25–100 mA cm(−2)) for electrocatalytic CO(2) reduction in aqueous media. The formation rate of formate reaches 1449 μmol h(−1) cm(−2) with 93% faradaic efficiency, the highest value reported to date. Our studies suggest that sulfur accelerates CO(2) reduction by a unique mechanism. Sulfur enhances the activation of water, forming hydrogen species that can readily react with CO(2) to produce formate. The promoting effect of chalcogen modifiers can be extended to other metal catalysts. This work offers a simple and useful strategy for designing both active and selective electrocatalysts for CO(2) reduction.