Synergistic effect of FeOOH cocatalyst and Al2O3 passivation layer on BiVO4 photoanode for enhanced photoelectrochemical water oxidation

BiVO ₄ is one of the most attractive photoanodes for water oxidation due to its 2.4 eV narrow band gap, suitable band edge position, good stability in aqueous solution, low cost and non-toxicity. However, due to some inherent disadvantages such as low carrier mobility, severe charge recombination and slow water oxidation kinetics, the actual BiVO ₄ photocurrent density is often lower than the theoretical value of 7.5 mA cm ⁻². In this paper, BiVO ₄ was modified by alkali-treated Al ₂O ₃ passivation layer and FeOOH, and the photocurrent density of BiVO ₄ reached an astonishing 3.8 mA cm ⁻² at 1.23 V _RHE, and the ABPE (applied bias photon-to-current efficiency) was close to 1 %. The detailed structural characterization and electrochemical test show that Al ₂O ₃ prepared by ALD (atomic layer deposition) can play a role in passivation of BiVO ₄ surface state after alkali treatment, inhibit electron hole recombination on BiVO ₄ surface, and accelerate hole transfer. As a hole storage layer and catalyst layer, FeOOH promoted the interfacial hole transfer, increased the active sites at the electrode electrolyte interface, and significantly increased the water oxidation activity. This work provides a novel method to enhance the performance of water electrolysis by using ALD to assist passivation of bismuth vanadate photoanode surface states.