CO ₂ is Converted into Renewable Energy and Green Products in a Membraneless Solar-Driven Fuel Cell

The urgent need for innovative renewable energy technologies and strategies to reduce greenhouse gas emissions is increasingly critical for global sustainability. Photocatalytic fuel cells (PFCs) present a promising solution by integrating solar energy harvesting with the direct and spontaneous conversion of chemical energy into electricity, not only achieving zero carbon emissions but also generating carbon credits. In this study, we developed BiVO4/WO3/V2O5 photoanodes and Cu2O/CuO photocathodes for a single-compartment, membraneless, solar-driven fuel cell that simultaneously converts CO2 and sulfite ions into electrical power and green fuels. Our optimized device achieved an open-circuit voltage of 0.50 V, a short-circuit current of 0.50 mA cm–2, and a maximum output power of 0.05 mW cm–2 at one sun illumination. We extensively characterized the photoelectrodes’ morphology and their structural, optical, and electronic properties to elucidate the PFC’s operating mechanism. The device primarily produced ethanol from CO2 reduction, followed by formate, acetate, and methanol as liquid products. In the gas phase, CH4 was the sole product from CO2 conversion, with a Faradaic efficiency (FE) of 40.8% at zero voltage bias, and hydrogen evolution accounted for only 0.5% FE. Overall, our PFC device demonstrates the capability to spontaneously generate renewable electric power and green fuels at ambient pressure and temperature, using solar energy as the only driving force.