Boosting the Photocurrent of the WO₃/BiVO₄ Heterojunction by Photoelectrodeposition of the Oxy-Hydroxide-Phosphates Based on Co, Fe, or Ni

Here we investigated the photoelectrodeposition of oxygen-evolving catalysts (OECs) based on oxy-hydroxides-phosphates of Co, Fe, or Ni (CoPi, FePi, and NiPi) on the WO₃/BiVO₄ heterojunction and their activity in water oxidation. The OECs were deposited by cycles of (i) open-circuit potential (OCP) and (ii) applying a potential positive enough to oxidize the metallic precursor on the WO₃/BiVO₄. The crystalline and optical properties of the photoanodes were not significantly affected by the OECs deposition. However, there was a remarkable increase in the photocurrent densities (j_pc) to water oxidation, where the modification with FePi showed the best result, achieving 2.12 mA cm^-2, which corresponds to 2.83 times higher than the heterojunction without the OECs. Furthermore, the OECs deposition changed the morphology of the heterojunction with the deposition of a thin film on its surface. In addition, during the FePi deposition, the BiVO₄ layer seems to partially dissolve. Our study shows a facile methodology to boost the activity of photoanodes to the water oxidation by photoelectrodeposition of OECs.

Keywords:
BiVO₄; WO₃; oxygen-evolving catalyst; water splitting; oxy-hydroxides metals