Photoanodes containing a WO3/BiVO4 heterojunction have demonstrated promising photoelectrochemical water splitting performance, but the ability to effectively passivate the WO3/BiVO4 interface has limited charge transport and collection. Here, the WO3/BiVO4...
Alkali metal (Na or K) doping in
BiVO4 was examined systematically for enhancing bulk charge
separation and transport in addition to improving charge transfer
from the surface. The alkali metal-doped BiVO4 thin film
photoanodes having nanostructured porous grain surface morphology
exhibited better photocurrent density than pristine BiVO4. In particular, Na:BiVO4/Fe:Ni/Co–Pi photoanode
showed a significantly improved photocurrent of 3.2 ± 0.15 mA·cm–2 in 0.1 M K2HPO4 electrolyte
at 1.23 V
RHE under 1 sun illumination.
The depth-dependent Doppler broadening spectroscopy measurements confirmed
the significant reduction in Bi- and V-based defect density with Na
metal doping, and this led to a higher bulk diffusion length of charge
pairs (four times that of the pristine one). Na doping led to reduced
surface defects resulting in improved surface charge transfer based
on cyclic voltammetry experiments. The density functional theory calculations
confirmed the improved performance in Na-doped BiVO4 photoanodes
achieved through interband formation and reduction in the band gap.
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