Interfacial interaction of Ag–MnOx heterostructure for efficient CO2 electroreduction to CO and aqueous Zn–CO2 batteries†

The electrocatalytic CO₂ reduction reaction (CO₂RR) to obtain valuable chemicals is an appealing way to ease the energy and environmental crises, but the development of efficient catalysts remains challenging. Herein, we report a novel Ag–MnO_x heterostructured catalyst and its high activity for the CO₂RR to CO. The obtained Ag–MnO_x exhibits a CO faradaic efficiency (FE_CO) of up to 97.5% at −0.8 V vs. reversible hydrogen electrode (RHE) and especially maintains an FE_CO above 90% within a broad potential window of 500 mV (−0.6 to −1.1 V vs. RHE). In addition, the CO₂RR performance was optimized using a flow cell, and the Ag–MnO_x catalyst reached a total current density of −255 mA cm⁻² at −2.0 V vs. RHE. Our designed in situ experiments and density functional theory (DFT) calculations reveal that the heterojunction interface formed between O-defect-rich MnO_x and active Ag enhances CO₂ adsorption and activation and simultaneously stabilizes the *COOH intermediate, thus leading to its superior catalytic performance. Furthermore, the Ag–MnO_x catalyst used as the cathode to assemble a Zn–CO₂ cell exhibited an ultimate power density of 13.63 mW cm⁻² and recharge time of over 65 h.