Photoelectrochemical water splitting using lithium doped bismuth vanadate photoanode with near-complete bulk charge separation

Abstract

Photoelectrochemical performance of BiVO4 photoanode is limited by poor light absorption, charge separation and transfer efficiencies. For the first time in the literature, Li doped nano-porous BiVO4 photoanode showed complete bulk charge separation efficiency (~100%) at 1.23 V vs RHE along with enhanced light absorption for water splitting. Li doping showed an increase (>20 times) in the photoelectrochemical water splitting compared to pristine BiVO4 photoanode. In particular, oxygen evolution catalyst was also employed for further improving the photoelectrochemical performance (4.2 ± 0.18 mA cm−2) of Li:BiVO4 photoanodes. The density functional theory calculations showing the formation of inter-band with band gap reduction due to interstitial Li doping in BiVO4 structure support enhancement in photoelectrochemical performance. In addition, Li doping in the BiVO4 lattice void positions led to a record photocurrent density of 7.3 ± 0.36 mA cm−2 at 1.23 V vs RHE in the presence of hole scavenger under one sun illumination. Further, present study systematically demonstrates role of Li in BiVO4 host for water oxidation through a detailed characterization and study of optical and charge transport properties.