Direct observation of the chemical transformations in BiVO4 photoanodes upon prolonged light exposure treatments

<p>Exposing BiVO₄ photoanodes to light pre-treatments leads to a significant photocurrent enhancement. The interpretation given for this phenomenon until now, has not taken into consideration the chemical nature of the processes taking place within the material. Here, we present a direct observation of the chemical transformations on the BiVO₄ surface upon prolonged light exposure and their implications on the photoelectrochemical oxidation of benzyl alcohol. Upon the light-aging treatment, structural characterization of our BiVO₄ shows a chemical segregation process of Bi species toward the surface of the photoanode. We found that this observation correlates with the formation of intra-band gap electronic states associated with oxygen vacancies, observed by impedance spectroscopy. Continuous infra-red wavelength excitation allowed us to monitor such oxygen vacancy states and, for the first time, to report infra-red steady-state photocurrent production in BiVO₄. Our results highlight the significance of the chemical nature of light-induced phenomena on metal oxide semiconductors and its implications when developing photosensitizers for photoelectrochemical applications</p>