Sharp Cu@Sn nanocones on Cu foam for highly selective and efficient electrochemical reduction of CO2 to formate

Abstract

Electrochemical reduction of aqueous CO₂ into formate is subject to poor selectivity and low current density with conventional Sn-based catalysts owing to the inert nature of CO₂ molecules and the low number of active sites. Recently, it has been demonstrated that alkali metal cations could greatly enhance selectivity for CO₂ reduction by stabilizing the key intermediates, which leads to an effective solution to this problem by concentrating local metal cations through tailoring the catalyst structure. Herein, we synthesized spiky Cu@Sn nanocones over a macroporous Cu foam, which has a curvature radius of 10 nm, via facile electrochemical coating of a thin layer of Sn over the Cu nanoconic surface. A faradaic efficiency of 90.4% toward formate production was achieved, with a current density of 57.7 mA cm⁻² at −1.1 V vs. a reversible hydrogen electrode, which far exceeds results achieved to date with state-of-the-art Sn catalysts. The performance should be attributed to the combined effects of a sharp conical feature that facilitates the enrichment of surface-adsorbed metal cations and the promotion of the mass transfer and active sites growth favored by the three-dimensional porous network.