Enhanced photoelectrochemical performance of Zr-doped BiVO4 photoanode deposited by co-sputtering

Zirconium (Zr) doped bismuth vanadate (BiVO₄) thin films were deposited on the fluorine-doped tin oxide substrate using a co-sputtering method to enhance the photoelectrochemical (PEC) performance. The radio frequency (RF) power of the ZrO₂ target, serving as a Zr source, was varied from 0 to 75 W to incorporate different amounts of Zr into BiVO₄, while RF power of the BiVO₄ target was maintained at 75 W. The presence of Zr in varying ratios within BiVO₄ thin film was confirmed by X-ray photoelectron Spectroscopy. Our study shows that the incorporation of a small amount of Zr into the monoclinic BiVO₄ structure improved the overall crystallinity of the thin film. However, higher levels of Zr doping led to a phase transition from the monoclinic scheelite to the tetragonal scheelite BiVO₄ structure, accompanied by the formation of other phase impurities, including the ZrV₂O₇ phase. Among the samples, the one deposited using 25 W RF power for the ZrO₂ target demonstrated the highest photocurrent, which was approximately five times higher than that of undoped BiVO₄. This enhancement is attributed to improved crystallinity, reduced electron–hole recombination, and optimized surface reaction areas by tuning grain sizes. Additionally, both undoped BiVO₄ and Zr-doped BiVO₄ photoanodes exhibited good stability during PEC reactions.