Engineering Cu-doped BiVO4 with enhanced charge separation for visible-light photocatalytic degradation of crystal violet and mixed cationic dyes.

The continuous discharge of dye-contaminated wastewater from industrial activities poses serious environmental challenges, necessitating the development of efficient and sustainable photocatalytic technologies. In this study, Cu-incorporated BiVO4 photocatalysts were synthesized via a hydrothermal method for enhanced visible-light-driven degradation of organic pollutants. Structural analysis verified the formation of monoclinic BiVO4 phase with successful Cu incorporation into the lattice, while the optimized 6% Cu-BiVO4 exhibited a cauliflower-like surface morphology having ∼18 nm average crystallite size. Cu incorporation effectively narrowed the band gap from 2.38 to 2.25 eV, boosting visible-light absorption and photocatalytic activity. Photoelectrochemical investigations revealed reduced charge-transfer resistance, enhanced charge separation, and suppressed electron-hole recombination after Cu modification. Under visible-light irradiation, 6% Cu-BiVO4 achieved 98% crystal violet (CV) degradation within 60 min, with the apparent reaction rate constant increasing from 0.0139 to 0.0553 min-1 compared with pristine BiVO4. Moreover, the catalyst demonstrated 95% degradation efficiency for a mixed-dye wastewater system within 75 min and retained 93% activity after three recycling cycles. Radical scavenging experiments identified (h+) as well as (˙O2 -) as the major reactive oxygen species responsible for pollutant degradation. The enhanced photocatalytic performance was attributed to Cu-induced band-gap modulation and efficient charge-carrier separation. These findings highlight Cu-engineered BiVO4 as a stable and promising photocatalyst for visible-light-driven wastewater purification.