Rechargeable Zn–CO2 Electrochemical Cells Mimicking Two-Step Photosynthesis

Metal–CO 2 batteries represent a promising priority for sustainable energy and the environment. However, CO 2 utilization in nonaqueous electrolytes mostly involves difficult CO 2 electrochemistry, leading to poor selectivity and limited cycle performance. Herein, an aqueous rechargeable Zn–CO 2 electrochemical cell that tunably produced CO fuel gas (90% Faradaic efficiency) during cell discharge (cathodic reaction: CO 2 + 2e − + 2H + → CO + H 2 O) and O 2 during cell charge at ≈2 V (cathodic reaction: H 2 O → 1/2O 2 + 2e − + 2H + ), mimicking the separate steps of CO 2 fixation and water oxidation during photosynthesis while exhibiting the advantages of high efficiency, tunable products, and operation independent of sunlight is proposed and realized. The cell achieves a remarkable energy efficiency of 68% with fuel generation, providing an alternative for the green, efficient, and safe utilization of CO 2 by metal–CO 2 batteries.