Unassisted Photoelectrochemical CO2 Conversion into Liquid Products by a Light-Responsive Gas-Diffusion Electrode

High Resolution Image Download MS PowerPoint Slide The combination of suitable semiconductors as photoelectrodes could sustainably provide unassisted CO 2 conversion using sunlight; however, few reports describe such achievement at this time. Herein, ethanol and formate were produced in a photoreactor assembled with a photoresponsive gas-diffusion electrode (GDE) containing Cu 2 WO 4 . The energy diagram, built from band gap energy and flat band potential ( E FB ) values, shows that the position of the Cu 2 WO 4 conduction band edge is suitable to promote CO 2 reduction in different products. BiVO 4 deposited on titanium foil was used as the photoanode; large-area Ti|BiVO 4 was successfully synthesized from the Ti|BiOI template; additional deposition of FeOOH/NiOOH decreased E FB and charge recombination, improving the photoanode performance for the O 2 evolution reaction. The CO 2 -fed GDE/Cu 2 WO 4 (7.5 cm 2 ) photocathode and the Ti|BiVO 4 /FeOOH/NiOOH (9.0 cm 2 ) photoanode were assembled in a H-type reactor containing NaHCO 3 aqueous solution. Under irradiation, these associated photoelectrodes supplied the thermodynamic requirements for a spontaneous current flow of 0.7 mA and, without any external bias, produced formate (16.5 μg h –1 cm –2 ) and ethanol (1.9 μg h –1 cm –2 ) at the cathode with solar-to-fuel efficiency of 0.07 and 0.005%, respectively. This photoreactor can be an inspiration for designing sustainable devices for CO 2 valorization using sunlight.