Introducing oxygen evolution promoting hole defect states at BiVO4 surface for enhanced photoelectrochemical activity

Doping metal ions offer a promising strategy to tune the intrinsic and surface properties of BiVO 4 for enhanced photoelectrochemical (PEC) activity. Given this, experimental and theoretical studies on cadmium (Cd) doping to BiVO 4 photoanode were studied for PEC water splitting applications. The spectroscopic and PEC results indicate that the substitution of Cd at Bi lattice sites causes the reduction in the valence state of V 5+ to V 4+ that creates hole trap states below the Fermi level of BiVO 4 . The introduced hole trap states at the BiVO 4 surface suppress the charge recombination and provide effective hole transfer sites for the facile water oxidation reactions. The Cd-BiVO 4 exhibited significantly higher photocurrent compared to the pristine BiVO 4 reaching 3.5 ​mA ​cm ₋2 (with a hole scavenger) at 1.23 ​V vs RHE. Furthermore, doping increases the carrier density in the bulk of BiVO 4 leading to improved charge separation, and charge transfer while reducing the hole transfer resistance at the interface. The Cd-doped BiVO 4 exhibited a charge separation efficiency of 80 ​% and with a 90 ​% of overall water splitting faradaic efficiency. Importantly, the results of this work propose the advantages of doping metal ions at Bi lattice sites in BiVO 4 for improved PEC activity.