Light-Driven Electrochemical Carbon Dioxide Reduction to Carbon Monoxide and Methane Using Perovskite Photovoltaics

Storing solar energy in chemical bonds is an effective strategy to overcome the intermittency of sunlight as an energy source. Here, we demonstrate unassisted light-driven electrochemical aqueous carbon dioxide reduction to carbon monoxide and methane using p-i-n double-cation lead halide perovskite solar cells in combination with catalytic electrodes for carbon dioxide reduction and water oxidation at near-neutral pH. Three series-connected photovoltaic cells and gold and ruthenium(IV) oxide electrodes provide carbon monoxide with >8% solar-to-carbon monoxide conversion efficiency for 4.5 h. Including concomitant hydrogen formation, the total solar-to-fuel conversion efficiency remains >8.3% for 10 h. Four series-connected cells with copper and ruthenium(IV) oxide electrodes provide methane. The longevity of the copper electrode improves by setting the cell to open circuit for 1 min every 15 min. The solar-to-methane conversion efficiency is close to 2%, and including 3% solar-to-hydrogen conversion efficiency, the solar-to-fuel conversion efficiency is 5% for 8 h.