SO42− mediated CO2 activation on metal electrode for efficient CO2 electroreduction

Abstract

The most difficulty of efficient CO2 electroreduction lies in the activation step that turns CO2 into the CO2− radicals or other intermediates that can be further converted. To overcome this bottleneck, many efforts have been devoted to develop electrocatalysts to lower the overpotential of CO2 activation, but they inevitably involve complicated or/and unscalable synthesis methods. Here we reported that the SO42− ion modified metal foils, including Zn, Ag, Au and Cu, demonstrated ∼6.5, 1.4, 14 and 2.5 times of CO faradaic efficiency in K2SO4 electrolyte compared to KHCO3 electrolyte at −1.05 V vs. RHE. According to both experimental and DFT studies, the electron-rich metal-SO4 adlayer can activate CO2 by bending the linear molecule of CO2 through donating electrons to the antibonding orbital of CO2, thus facilitating the formation of key intermediate *CO2−. Moreover, the adsorption of H+ on metal sites is restrained by the metal-SO4 adlayer, leading to a suppressed H2 evolution activity. From a broader perspective, many catalysts can benefit from this approach to achieve more efficient CO2 electrochemical reduction.