A large-sized cell for solar-driven CO2 conversion with a solar-to-formate conversion efficiency of 7.2%

Solar-driven electrochemical (EC) reduction of CO2 to fuel using photovoltaic (PV) cells is a promising CO2 recycling technology. However, the scale-up of EC reactors lowers the solar-to-chemical conversion efficiency (eta(STC)) due to the large electric resistance of the electrode catalysts and an insufficient supply of reactants. We designed a large-sized cell to convert CO2 to formate. It consists of five stacked electrodes (electrically parallel connected) and six series-connected single-crystalline Si PV cells (area similar to 1,000 cm(2)). Low-resistivity anodes loaded with IrOx and cathodes loaded with Ru complex polymer on carbon support operate without a membrane between them at a low voltage of 1.85 V. They generate a reaction current of 6.30 A, owing to the homogeneous flow of the CO2-dissolved electrolyte to achieve a sufficient CO2 supply and a good match between the PV and EC performances. The cell yields a conversion efficiency of 7.2% and the high production rate of 93.5 mmol/h.