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

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.