Highly selective electrochemical CO2 reduction to CO using a redox-active couple on low-crystallinity mesoporous ZnGa2O4 catalyst

Abstract

The substantial overpotential of CO₂ activation, the complex CO₂ reduction pathway, and the competitive H₂ evolution reaction (HER) limit the practical applications of CO₂-based electrochemical energy conversion and storage technologies due to their low energy efficiency and product selectivity. Here, we proposed a strategy that combines mesopores and redox-active couple to effectively capture CO₂ and selectively generate CO product. As an example, we construct a redox-active couple, Zn²⁺/Zn⁺, on the low-crystallinity mesoporous ZnGa₂O₄ electrocatalyst. The mesopores not only help to capture CO₂ effectively but also inhibit the H₂ evolution. The weak lattice constraint of low crystallinity benefits the formation of a Zn²⁺/Zn⁺ redox couple to strongly interact with CO₂ molecule for subsequent activation and catalytic conversion, thus effectively decreasing the activation energy of CO₂ to the active species CO₂⁻ and accelerating the proton transfer to form the crucial COOH* intermediate. Consequently, this catalyst exhibited a high faradaic efficiency of 96% among Zn-based electrodes for CO generation at the relatively low applied potential of −1.4 V vs. Ag/AgCl (−0.8 V vs. RHE), and excellent stability during 10 h operation in a 0.1 M KHCO₃ solution.