Nickel ion doping induced enhancement in photocatalytic degradation efficiency of tin oxide nanoparticles towards mineralization of Reactive Blue 19 textile dye

In this study, pure and nickel-doped tin oxide (SnO₂) nanoparticles were successfully synthesized via wet-chemical method to investigate their structural, optical, and photocatalytic properties, with a focus on enhancing its photodegradation efficiency for decomposing Reactive Blue 19 (RB 19) dye under UV-Vis light irradiation. Field emission scanning electron microscopy (FESEM) analysis revealed that Ni doping significantly influenced the surface morphology of SnO₂, increasing surface roughness. Energy-dispersive analysis of X-rays (EDAX) spectroscopy and elemental mapping analysis confirmed uniform and successful incorporation of Ni²⁺ into the SnO₂ lattice. X-ray diffraction (XRD) study indicated that all samples retained the tetragonal rutile structure, with no secondary phases, confirming substitutional doping. A reduction in crystallite size and minor peak shift for the doped samples suggested a minimal lattice distortion and increased microstrain due to Ni incorporation. UV–Vis absorption spectra showed strong UV absorption in pure SnO₂, which slightly red-shifted for Ni-doped samples, indicating band gap narrowing due to sp–d exchange interactions and the formation of localized energy states. These modifications, along with the generation of oxygen vacancies, improved visible-light responsiveness. Photocatalytic experiments showed that Ni-doped SnO₂ significantly outperformed pure SnO₂ in degrading RB 19 dye, following pseudo-first-order kinetics. Enhanced performance of the Ni-doped samples was attributed to improved charge separation and increased active surface sites. Optimal catalytic activity of 90.64 % was also achieved at lower photocatalyst loading concentration. The recyclability tests confirmed over 83.44 % efficiency retention after four cycles. These findings highlight the potential of Ni-doped SnO₂ as a stable and efficient photocatalyst for wastewater treatment applications. • SnO 2 and Ni doped SnO 2 nanoparticles are prepared by sol-gel method as confirmed by XRD • Ni doping modifies SnO₂ surface morphology increasing roughness • Ni doping narrows band gap and enhances light response via sp–d interactions • Ni–SnO₂ achieves 90.64 % RB 19 degradation with high stability over multiple cycles