Boosting the photoelectrochemical performance of BiVO 4 by borate buffer activation: the role of trace iron impurities.

BiVO 4 is an attractive photoanode material for water oxidation, but requires surface treatment to improve the energy efficiency and stability. Herein, we investigate the role of borate buffer in activating the BiVO 4 photoanode. We found that trace iron impurities in the borate buffer play a critical role in activating the photoanode. By optimizing the activation conditions, the photocurrent density attains 4.5 mA cm -2 at 1.23 V RHE without any cocatalysts, alongside a high ABPE value of 1.5% at 0.7 V RHE . Our study discloses the role of iron in the activation effect of borate buffer on the BiVO 4 photoanode, which has implications for other catalytic systems.