Polydopamine-mediated hydrogen bond network promotes hole extraction in BiVO4 photoanodes for efficient photoelectrochemical water oxidation†

Efficient migration of photogenerated holes is a critical factor influencing the photoelectrochemical water oxidation performance of BiVO₄. Herein, the hole transport capacity of BiVO₄ photoanodes was significantly enhanced by introducing a natural bio-polymer, polydopamine (PDA), as a hole transport layer (HTL). Experimental analyses and theoretical calculations confirm that the interfaces between PDA and BiVO₄ is bonded through hydrogen bonds (O–H⋯O). This hydrogen bonding serves as an efficient hole transport channel, optimizing the hole transfer barrier and inducing charge redistribution at the interface, thereby generating an interfacial electric field (EF). Furthermore, a β-FeOOH cocatalyst is formed through a simple oil bath mineralization strategy, which acts as an effective OER catalyst to promote the charge transport processes and optimize the interfacial reaction kinetics. Consequently, the judiciously designed BiVO₄/PDA/β-FeOOH photoanode renders an exceptional performance with a photocurrent density of 4.84 mA cm⁻² at 1.23 V_RHE as well as a charge separation efficiency of 80.9% and a charge injection efficiency of 79.6%. The introduction of the PDA HTL not only passivates surface defects but also significantly improves light stability. We believe this work gives a new insight into the application of natural bio-polymer decorated photoanodes in photoelectrochemical systems.