Structure-property-performance correlation in BiVO4 photoanodes synthesized by intensity-tuned pulse electrodeposition.

The development of efficient and stable photoanodes is critical for advancing photoelectrochemical (PEC) water splitting technologies. In this work, bismuth vanadate (BiVO4) photoanodes were fabricated using a two-step method combining the pulse electrodeposition of bismuth and spin-coating of a vanadium precursor [VO(acac)2], followed by thermal annealing. By systematically varying the pulse voltages and vanadium precursor volume, a series of samples were produced. The sample labeled Bi-576 (deposited at 1.5-1.7 V with 0.6 μL VO(acac)2) exhibited the highest PEC performance. This optimized sample achieved a photocurrent density of 1.33 mA cm-2 at 1.23 V vs. RHE, with an applied bias photon-to-current efficiency (ABPE) of 20% and a charge injection efficiency of 60.1% under AM 1.5G illumination. Structural analysis via X-ray diffraction revealed a preferential (121) crystal orientation and reduced crystallite size, promoting directional charge transport and suppressing recombination. Raman and X-ray photoelectron spectroscopy confirmed the presence of Bi3+, V5+, and strong V-O bonding, along with surface oxygen species that enhance charge separation and interfacial transfer. Field-emission scanning electron microscopy showed a porous, interconnected morphology that increased the electrochemical active surface area (ECSA). Electrochemical impedance spectroscopy and Mott-Schottky analysis revealed a high donor density of 8.65 × 1020 cm-3 and a long interfacial time constant (τ int) of 31.46 ms, both contributing to efficient charge transport. Stability tests showed that Bi-576 retained over 82% of its photocurrent after 10 hours of continuous operation, indicating excellent long-term durability. These results demonstrate that tuning the pulse deposition conditions and precursor chemistry enables the rational design of BiVO4 photoanodes with optimized structural and electronic properties. This scalable approach offers a promising route for the development of high-performance photoanodes for solar-driven water splitting.