Fabrication and Performance Validation of BiVO4 Photoanode-Based Prototype Photoelectrochemical Cells with Different Sizes and Reducing the Photocurrent Density Loss with Different Conductive Patterns

Solar water splitting seems promising for green hydrogen production, but it is still at the lab-scale level with TRL values of 1–3. Among various solar water splitting techniques, photoelectrocatalytic (PEC) water splitting is a viable and emerging technology for large-scale application with the utilization of various photoelectrodes, in which bismuth vanadate (BiVO4) is considered a promising material for photoanode fabrication due to its narrow band gap (∼2.4 eV) and a higher solar-to-hydrogen (STH) efficiency of ∼9.2%. With this perspective, in this present work, large-area BiVO4 electrodes with different dimensions (1, 4, 9, 16, and 25 cm2) were fabricated via a facile electrodeposition method, followed by chemical–thermal treatment, and the PEC performances of scaled-up photoanodes were investigated under the illumination of AM 1.5G (30 mW cm–2). From the investigation, it is clear that by increasing the area of the BiVO4 photoanode, the photocurrent density was reduced stepwise due to the resistance in the FTO substrate. The activity of large-area BiVO4 was enhanced by the incorporation of a Ag-conductive line; moreover, the effect of different Ag line patterns (line and grid) was also investigated. Among them, BiVO4 (25 cm2-Grid) delivered a photocurrent density of 0.21 mA cm–2 at +1.23 VRHE, which is 1.5-fold higher than BiVO4 (25 cm2). Further, the large-area (25 cm2) photoanode was investigated toward sulfite oxidation; compared to water oxidation, the loss in the activity is reduced. BiVO4 (25 cm2-Grid) delivered a photocurrent density of 0.61 mA cm–2, which is ∼3-fold higher than the water oxidation. Hence, the prototype PEC cell was constructed with BiVO4 (25 cm2-Grid) for hydrogen production via sulfite oxidation, which delivers a theoretical H2 production rate of ∼225 μmol h–1 (∼9 μmol cm–2 h–1) at +1.0 VPt under the illumination of AM 1.5G (30 mW cm–2). From these results, it is claimed that sulfite oxidation is more effective than water oxidation for large-scale green hydrogen production.