Effect of Operating Conditions on the Degradation of BiVO 4 Photoanodes

Abstract This work investigates how irradiance, temperature, and electrolyte properties (pH, concentration, and flow rate), influence the degradation of spray‐pyrolyzed BiVO 4 photoanodes during water splitting for solar fuel production. A novel four‐cell photoelectrochemical (PEC) array coupled to Fresnel lenses and a water bath allowed for careful control of the operating conditions and to decouple their individual contributions toward the degradation of BiVO 4 films. Time‐resolved ex situ characterization of the films is performed at different stages of degradation, alongside impedance spectroscopy under a wide range of atypical and seldom‐reported operating conditions. To deconvolve the interplay of the different operating conditions, a 1D phenomenological model is used to estimate the degradation fraction. This proposed figure of merit is defined as the ratio between the charge that contributes toward the dissolution process and the total charge transferred during photoelectrochemical water splitting. The model is successfully validated by detailed material characterization, utilizing scanning electron microscopy (SEM), energy dispersive X‐ray (EDX), X‐ray photoelectron spectroscopy (XPS), and X‐ray diffraction (XRD) analyses across different stages of degradation. It is observed that increasing the irradiance, temperature, and electrolyte concentration can significantly impair the stability of the films. However, operating under higher irradiances also translates into a more effective charge transfer at the photoanode | electrolyte interface. The findings presented here have practical implications for designing and selecting operational strategies to realize efficient and stable solar fuel production.