Thermodynamic and Kinetic Control of Photoelectrochemical CO2 Reduction into Liquid Fuels

Abstract

In the photoelectrochemical CO2 reduction reaction, water oxidation reaction is performed on 040-BVO and chemical fuels is obtained on Cu cathode in the CO2-saturated NaCl electrolyte under AM 1.5 G. C1 chemical fuel is evolved through reduction potential depending multistep process from CO2 molecule. 040-BVO(photoanode)/NaCl(electrolyte)/Cu(cathode) system is illuminated with solar light under the external bias that is tailored to reduce CO2 via reduction potential tuning. Integrating applied bias potential into conduction band minimum of 040-BVO enables CO2 molecules to be converted into valuable chemical fuels. We observe that the selectivity and yield of the products depend on CO2 reduction potential tuning. With water oxidation reaction of 040-BVO photoanode which has 42.1% of the absorbed photon-to-current conversion efficiency at 1.23 V (vs RHE), chemical products were observed as faradaic efficiency of 30% formic acid, 60% formaldehyde, 12% MeOH and 3% EtOH by reduction potential tuning. For this study, the correlation between the production of solar chemical fuels and CO2 reduction potential tuning via external bias potential on 040-BVO photoanode/Cu photocathode is systematically investigated. Keywords: Artificial photosynthesis; Multi-electron shuttling; CO2 reduction potential tuning