Enhanced Photocatalytic Degradation of Congo Red Dye Using Nickel-Doped TiO2 Nanoparticles Synthesized by Glycerol-Assisted Co-Precipitation: A Comparative Study with Pure TiO2

Abstract

Photocatalytic degradation of Congo Red (CR) dye is investigated using annealed (600 °C) TiO₂ and nickel-doped (Ni-doped) TiO₂ nanoparticles (NPs) with doping concentrations 3%, 6%, and 9% as catalysts, synthesized by glycerine-assisted co-precipitation method with microwave irradiation. The morphological, thermal, and optical characterisations of the samples are examined using various material characterization methods. Undoped TiO₂ NPs annealed at 600 °C exhibit a bandgap energy 3.13 eV, which decreases to 2.48 eV,2.46 eV, and 2.23 eV for 3%,6% and 9% Ni-doped TiO₂ NPs, respectively, under the same annealing conditions. 30 mg catalyst dosage is used under 120 min of UV irradiation to investigate the photocatalytic degradation efficiency of CR dye at pH 5. Among different treatments, the 9% Ni-doped TiO₂ NPs (annealed at 600 °C) exhibit the highest degradation efficiency (99.5%), while the 3% and 6% Ni-doped TiO₂ NPs show degradation efficiencies 98.9% and 99.2%, respectively. Regression analysis is performed to evaluate the suitability of the models and the resulting statistical parameters confirm their reliability in predicting the photocatalytic activity. The CR degradation efficiency of 9% Ni-doped TiO₂ NPs annealed at 600 °C remains at 97.3% after the fourth cycle, indicating good catalytic stability. Future studies may focus on heterojunction coupling strategies to achieve complete photocatalytic degradation and stability of Ni-doped TiO₂ NPs.