Atomic Insight into the W-Doping Effect on Carrier Dynamics and Photoelectrochemical Properties of BiVO 4 Photoanodes

BiVO 4 has become the top candidate for photoanode materials in the light-driven water-splitting reaction. However, its overall efficiency for water splitting still remains well below its theoretical limit. Further development of these materials has been hampered by the lack of knowledge concerning key factors that guide the carrier transport and separation. In this work, we report the effect of W doping on the electronic structure, carrier dynamics, and photocurrent performance of BiVO 4 photoanode. Using X-ray absorption spectroscopy, we show that the dopants occupy the V sites, which leads to the reduced Bi-ligand distances and less distorted local structure at Bi center. Using transient absorption spectroscopy, we found that doping altered the hole traps significantly, which inhibits carrier recombination and increases the electron lifetime in the doped film. Compared to the undoped BiVO 4 film, the photocurrent of the doped film shows a significant increase while limited difference of photocurrents under back and front illumination was observed. These results suggest that the reduced dimension and less distorted local structure at Bi center favorably extend the electron lifetime by dramatically altering the nature of the trap states, which plays a major role in improving the photoelectrochemical performance of BiVO 4 film.