Packaging BiVO₄ nanoparticles in ZnO microbelts for efficient photoelectrochemical hydrogen production

Constructing semiconductor heterojunction with optimal structure and composition is highly desired to maximize the solar light utilization for photoelectrochemical (PEC) water splitting. Here, we reported the fabrication of BiVO₄@ZnO heterojunction with a novel nanostructure for PEC water splitting via foaming-assisted electrospinning and subsequent atomic layer deposition (ALD) techniques. In such BiVO₄@ZnO heterojunction, the isolated BiVO₄ nanoparticles were packaged within the ZnO microbelt matrix. During PEC water splitting, the BiVO₄ acts as the primary light absorber for wider solar spectral harvesting, and the ZnO prompts the transfer of the photo-excited high-energy electrons, which would render them with prolonged lifetime and enhanced separation of the photogenerated charge carriers. In addition, the microbelts architecture with a hollow channel can also effectively improve the interfacial charge separation and transportation. Accordingly, the PEC performances of BiVO₄@ZnO hybrid microbelts were significantly enhanced with a photocurrent density up to ∼0.46 mA cm⁻² (at 1.23 V vs. reversible hydrogen electrode (RHE) under simulated sunlight illumination), which is 15.3 times to that of pure BiVO₄ counterpart (∼0.03 mA cm⁻²). The photocurrent density of the BiVO₄@ZnO electrode can be further increased to 1.07 mA cm⁻² at 1.2 V vs. RHE by adding hole scavenger (NaSO₃) in the electrolyte solution under AM 1.5 G irradiation.