Unveiling the activity and stability of BiVO4 photoanodes with cocatalyst for water oxidation

Developing low-cost and efficient cocatalyst is highly desirable for photoelectrochemical (PEC) water oxidation. FeOOH is one of the most typical cocatalysts, the active sites of FeOOH in PEC remain unclear. Herein, the FeOOH was deposited on BiVO 4 photoanodes through electrodeposition. A series of experimental evidence shows that the Bi–O–Fe bond is beneficial to the improvement of water oxidation activity, while the FeOOH can not restrain the dissolution of V 5+ and improve the stability of the photoelectrode. In order to further improve the activity and stability of BiVO 4 /FeOOH photoanode, a low-cost metal-organic coordination composed of tannic acid coordinated with Ni ions (TANi) was assembled on the BiVO 4 /FeOOH (denoted as BiVO 4 /FeOOH/TANi). Under AM 1.5 G illumination, an impressive current density of 4.6 mA cm −2 (1.23 V vs. RHE) was obtained for BiVO 4 /FeOOH/TANi photoanode. Systematic studies reveal that the enhanced PEC activity comes from the protection of BiVO 4 and enhancement of charge separation efficiency. This work provides a strategy for designing cocatalysts to construct efficient and stable PEC water oxidation. 1. The photocurrent density of BiVO4/FeOOH/TANi is 4.6 mA cm −2 at 1.23 V vs. RHE. 2. The formed Bi–O–Fe bond contributes to enhancing the PEC activity of BiVO4. 3. The TANi significantly improved the stability of the photoelectrode. 4. The maximum ABPE value of BiVO4/FeOOH/TANi reaches up to 1.3% at 0.71 V vs. RHE.