Experimental Evidence for Photoactivated BiVO₄ Anodes with Enhanced Photoelectrochemical Water Oxidation

Abstract

High Resolution Image Download MS PowerPoint Slide Photoactivated bismuth vanadate (BiVO 4 ) anodes are highly promising candidates for solar-driven water splitting. Extant research has shown that prolonged light exposure results in the formation of a borate cocatalyst junction layer on the BiVO 4 anode surface, which is attributable to the photocorrosion of BiVO 4 and etching modification in a borate electrolyte; consequently, the photocurrent is significantly increased. This study analyzes the effects of light alone on photoactivated BiVO 4 anodes in the absence of the borate cocatalyst. We utilized photocorrosion- and etching-resistant BiVO 4 to prevent formation of the borate cocatalyst overlayer and investigated the effects of short-duration light irradiation on the photoelectrochemical (PEC) properties. Remarkably, we observed that pretreatment with a mere 20 min of light exposure in both air and electrolyte resulted in a notable increase in the photocurrent. In addition, this photoactivation effect recurred via repeated light irradiation and dark storage. The PEC technique was used to show that the intraband gap states reduced after photoactivation, and hole accumulation increased on the photoactivated BiVO 4 surface during the subsequent water oxidation reaction. Furthermore, the spectroelectrochemical spectra revealed that the hole-trapping absorbance of photoactivated BiVO 4 decreased. Photoincident absorption spectroscopy and transient absorption spectroscopy further showed an increased population of the photogenerated holes and an extended lifetime on the microsecond time scale, respectively, which contributed to improved PEC water-splitting activity with the photoactivated BiVO 4 . These findings are expected to offer deeper insights into the trap-filling mechanism underlying BiVO 4 photoactivation and its effect on PEC water splitting.

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