Ethanol vapor-driven multi-carbon chemistry enables high-performance Mg-CO2 battery

Recent advancements in metal-CO2 batteries with enhanced energy efficiency in a sustainability manner largely rely on catalytic improvements to accelerate the sluggish kinetics of CO2 reduction and evolution reactions (CO2RR/CO2ER) occurring at the multiphase interface. However, conventional solid and liquid catalysts often increase the adsorption of both reactant gas and solid-phase discharge products, lowering discharge overpotentials but impeding product decomposition during charging. This trade-off complicates efforts to simultaneously reduce charge-discharge overpotentials and improve overall battery efficiency. Here, we introduce an ethanol vapor-driven strategy for Mg-CO2 batteries—distinct from traditional solid and liquid catalysis—that selectively enhances CO2 adsorption while limiting the adsorption of discharge products. This approach enables high energy efficiency through the formation and decomposition of the first conductive organic multi-carbon (C2+) product in metal-CO2 batteries, specifically Mg(CH3COO)2·4H2O. The Mg-CO2 battery delivers outstanding discharge and charge capacities beyond 50,000 mAh g−1, coupled with stable cycling over 600 h, ranking it the best Mg-CO2 systems reported to date. This catalyst-free strategy for multi-carbon production holds potential for applications in CO2 reduction and carbon fixation.