Rechargeable Zn-CO2 Electrochemical Cells Mimicking Two-Step Photosynthesis.

Metal-CO2 batteries represent a promising priority for sustainable energy and the environment. However, CO2 utilization in nonaqueous electrolytes mostly involves difficult CO2 electrochemistry, leading to poor selectivity and limited cycle performance. Herein, an aqueous rechargeable Zn-CO2 electrochemical cell that tunably produced CO fuel gas (90% Faradaic efficiency) during cell discharge (cathodic reaction: CO2 + 2e- + 2H+ → CO + H2 O) and O2 during cell charge at ≈2 V (cathodic reaction: H2 O → 1/2O2 + 2e- + 2H+ ), mimicking the separate steps of CO2 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 CO2 by metal-CO2 batteries.