Computational Design of Optimized Modular Photovoltaic Electrochemical Reactor for Energy Efficient CO₂‐to‐Cn Reduction Reaction with Bandgap Tunable Perovskite Tandem Cells

For electrosynthesis of carbon fuels from CO 2 , engineered catalysts have improved the electrochemical (EC) reduction efficiency. However, most EC systems rely on a batch reactor, which is not relevant for C n fuels with high n ( n ≥ 3) due to low selectivity. For enhanced electron‐to‐fuel (ETF) efficiency, modular configurations are advantageous. The best configurations allowing high yield reduction of CO 2 into C n fuels are investigated. It is found that serial and parallel configurations exhibit four to five times higher ETF efficiency than simple batch reactor. The best photovoltaic (PV) tandem cells made of metal halide perovskite for the optimized EC modular systems are also found. These materials have a bandgap tunability covering most C n fuels. With the computationally optimized tandem PVs, it is found that the [PV+EC] series configuration achieves up to 2.28% and 2.86% solar‐to‐fuel (STF) efficiency of C 3 aldehydes and alcohols, which are greater than what has been reported in the literature. For C 4 aldehydes and alcohols, the [PV+EC] parallel configuration achieves up to 0.17% and 0.21% STF efficiency, respectively. The present study on modules and materials design will provide a useful way to create EC production of C n fuels that can help reach carbon neutrality.