Serial hole transfer layers for a BiVO 4 photoanode with enhanced photoelectrochemical water splitting

In this paper, a high-performance BiVO4 photoanode deposited with serial hole transfer layers was fabricated for photoelectrochemical (PEC) water splitting in order to overcome the shortcomings of pure BiVO4 electrodes in terms of poor charge transport properties and undesirable surface water oxidation kinetics. The hole transfer layer of Fe2O3 was first deposited on the surface of pure BiVO4 to promote the hole transfer from the bulk of the semiconductor to the electrode surface (bulk/surface transfer process), and then the hole transfer layer of NiOOH/FeOOH was deposited on the surface to improve the hole transfer from the electrode surface to the electrolyte (surface/electrolyte transfer process). The results showed a remarkable improvement in PEC water splitting performance for the NiOOH/FeOOH/Fe2O3/BiVO4 photoanode. The photocurrent was up to 2.24 mA cm-2 at 1.23 V vs. RHE, which was about 2.95 times that of the pristine BiVO4 photoanode. Meanwhile, the charge transport efficiencies in the bulk (ηbulk) and the surface (ηsurface) were enhanced by 1.63 and 2.62 times compared to those of the BiVO4 photoanode at 1.23 V vs. RHE, respectively. In addition, the novel photoanode was assembled with a commercial silicon PVC for self-bias PEC water splitting, and a stable photocurrent density of ∼2.60 mA cm-2, corresponding to a ∼3.2% STH conversion efficiency, was achieved spontaneously. Our study provided a more efficient serial hole transfer strategy for achieving a BiVO4 photoanode with enhanced PEC water splitting.