Zr doping of BiVO₄ thin film via co-sputtering is explored as a possible solution to overcome BiVO₄'s fast carrier recombination, resulting in low carrier mobility(0.044cm²v^-1s^-1) and a short hole diffusion length. Therefore, understanding the dopant effects is crucial for enhancing device performance. The photoelectrochemical (PEC) photocurrent density exhibited an increase that peaked at approximately 50w of RF power applied to the ZrO₂ target and a gradual decrease in the photocurrent density as the RF power was further increased. The increase in photocurrent density up to approximately 50w of RF power can be attributed to the optimized Zr replacing Bi, which contributes to generating the donor state, promoting the separation and efficient transport of charge carriers.[1] However, beyond the optimal doping concentration of 50w, a gradual decrease in the photocurrent density was observed. This decrease can be due to the crystal phase transition from monoclinic-scheelite to tetragonal scheelite and tetragonal zircon [2] at doping concentrations above 50w power. This indicates that maintaining the monoclinic-scheelite phase is essential for enhancing photocatalytic activity. Therefore, Zr doping, within a specific threshold where the monoclinic-scheelite phase is maintained, can enhance the photocatalytic activity for oxidation. The findings from this study contribute to understanding the fundamental aspects of Zr-doped BiVO₄ thin films for developing efficient photocatalytic systems for water splitting.