Enhancement of visible light-induced photocatalytic degradation of tetracycline through highly efficient NiO/TiO2 p-n heterojunction catalysts

The current study focuses on the development of highly efficient nickel oxide/titanium dioxide (NiO/TiO₂) p-n heterojunction catalysts constructed via sol–gel and ultrasonic techniques. Different techniques, including XRD, SEM, EDS mapping, and XPS, confirmed the successful synthesis of the photocatalysts. The BET analysis showed that the NiO/TiO₂ heterojunction has a surface area of 107.52 m²/g compared to pure NiO and TiO₂ (75.37 m²/g and 89.13 m²/g) respectively. The catalyst was then implemented to decompose the antibiotic tetracycline (TC) in water under visible light. The outcomes revealed that the degradation rate of TC reached 97.69 % using NiO/TiO₂, which is substantially greater than the degradation achieved with pure NiO (52.43 %) and TiO₂ (71.11 %) within a 48-minute period pursuant to the most favorable circumstances. The initial rate constant of the NiO/TiO₂ (0.0756 min⁻¹) was significantly higher compared to that of the NiO (0.0153 min⁻¹) and TiO₂ (0.0261 min⁻¹). The lower bandgap energy of the NiO/TiO₂ (3.19 eV) catalyst compared to the pure NiO (3.58 eV) and TiO₂ (3.29 eV) facilitated the abatement of TC due to the improved harvesting of visible light absorption. Furthermore, the study investigated the impact of several different reaction parameters and intervening anions on TC degradation. Radical trapping investigations substantiate the existence of reactive oxygen species. In addition, NiO/TiO₂ catalyst exhibited extraordinary stability and maintained its catalytic efficiency despite enduring five successive cycles. Overall, the NiO/TiO₂ catalyst demonstrated remarkable potential for abolishing TC-contaminated water.