Photosynthesis of formate from CO2 and water at 1% energy efficiency via copper iron oxide catalysis†
Solar conversion of carbon dioxide and water to value-added chemicals remains a challenge. A number of solar-active catalysts have been reported, but they still suffer from low selectivity, poor energy efficiency, and instability, and fail to drive simultaneous water oxidation. Herein, we report CuFeO2 and CuO mixed p-type catalysts fabricated via widely employed electroplating of earth-abundant cupric and ferric ions followed by annealing under atmospheric air. The composite electrodes exhibited onset potentials at +0.9 V vs. RHE in CO2-purged bicarbonate solution and converted CO2 to formate with over 90% selectivity under simulated solar light (air mass 1.5, 100 mW cm−2). Wired CuFeO2/CuO photocathode and Pt anode couples produced formate for over 1 week at a solar-to-formate energy conversion efficiency of ∼1% (selectivity >90%) without any external bias while O2 was evolved from water. Isotopes and nuclear magnetic resonance analyses confirmed the simultaneous production of formate and O2 at the stand-alone couples.