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.