Boosting Photoelectrochemical Water Oxidation Activity and Stability of Mo-Doped BiVO₄ through the Uniform Assembly Coating of NiFe–Phenolic Networks

Photocorrosion is a key factor that greatly hinders the stability of photoanodes. Depositing appropriate cocatalysts can effectively protect the semiconductors from photocorrosion as well as improve the photoelectrochemical (PEC) activity. However, the formation of cocatalysts occurs mostly under island growth, making the semiconductors partially unprotected, thus leading to poor stability. Herein, we demonstrate the complex assembly film composed of phenolic ligands (tannic acid) coordinated with Ni and Fe ions (TANF) as a robust cocatalyst for Mo-doped BiVO4 (Mo:BiVO4@TANF) toward PEC water oxidation. The photocurrent density of Mo:BiVO4@TANF at 1.23 V versus reversible hydrogen electrode (RHE) reaches a value of 5.10 ± 0.13 mA cm–2. Furthermore, because the complete coverage of the TANF film can effectively protect the semiconductor from photocorrosion, 92% photocurrent of the integrated photoanode is retained after operating at harsh 1.23 V vs RHE for 3 h. The outstanding activity and stability of the integrated photoanode surpass those of many existing cocatalysts such as ferrihydrite (Fh) and cobalt phosphate (Co-Pi). In addition, the TANF cocatalyts can be also applied to other semiconductors (nondoped BiVO4 and TiO2), indicating the TANF is a promising cocatalyst alternative for solar energy conversion.