Unveiling BiVO4 photoelectrocatalytic potential for CO2 reduction at ambient temperature

Abstract

Here, we explore monoclinic BiVO₄ as a cathode in a photoelectrochemical (PEC) system for CO₂ reduction (CO₂R). The catalyst was prepared using a simple oxidant peroxide method with crystallization under hydrothermal conditions, and subsequently sprayed on the FTO substrate. CO₂R was carried out in an inflow and sealed electrochemical system for 6 h. The best performance was found to be under photoelectrocatalysis powered by a light-emitting diode (LED) as an illumination source when compared to photocatalysis (using different halogen UV and LED illumination), electrocatalysis, and photoelectrocatalysis powered by a halogen UV illumination source, with total production values of 22 and 5.5 μmol cm⁻² for methanol and acetic acid, respectively. This achievement occurs because, even though BiVO₄ as a photocatalyst does not have sufficient potential to drive CO₂R, an external potential can be applied to drive the reaction. Moreover, the photogenerated electron–hole pairs are guided by the external potential, improving the charge separation and promoting the rapid electron transfer to reduce CO₂ on the photoelectrocathode at a lower overpotential when compared to electrocatalysis. LED illumination produced higher amounts of products than UV illumination because UV light affects the catalyst surface altering the number of catalytic sites available for the reaction and reducing their performance.