Low full-cell voltage driven high-current-density selective paired formate electrosynthesis

Abstract

Anodic selective electro-oxidation of methanol paired with cathodic carbon dioxide (CO₂) reduction is regarded as a promising strategy to generate value-added formate products. We first design a 3D-assembled NiCo layered double hydroxide electrocatalyst containing sulfur with a low coordination number (S–NiCo-LDH) for methanol oxidation to formate. We decrease the anodic methanol-to-formate working potential to 1.39 V (vs. RHE) at 100 mA cm⁻², and maintain ∼100% formate faradaic efficiency at a high current density up to 300 mA cm⁻² with >60 mV, lower than the previous best potentials in the literature. From the remaining S 2p_1/2 peak after electrocatalysis, we demonstrate that the low-coordinated sulfur on the catalyst surface serves as the promoter for the reaction. In the end, when combining the CO₂ reduction in the cathode, we achieve a record low full-cell voltage of 2.48 V to drive selective paired formate electrosynthesis at a high current density of 300 mA cm⁻².