Structure–Property–Performance Correlation in BiVO₄ Photoanodes Synthesized by Intensity-Tuned Pulse Electrodeposition

Abstract

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 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 BiVO₄–576 (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 electrochemically 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 (τint) of 31.46 ms, both contributing to efficient charge transport. Stability tests showed that BiVO₄–576 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.