Microwave-engineered TiO2/NiTiO3 heterojunctions for superior solar photocatalytic remediation of azo dyes

In this study, heterojunction nanostructures S1-TiO2 and S2-TiO2/NiTiO3—were successfully synthesized via a microwave-assisted solution combustion technique. The heterojunction nanostructures were comprehensively characterized to assess their physicochemical properties relevant to photocatalysis. Structural and morphological analyses using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDAX), and Brunauer–Emmett–Teller (BET) surface area measurements confirmed the formation of well-crystallized materials. XRD results revealed an average crystallite size of approximately 30 nm. UV–Vis diffuse reflectance spectroscopy (UV-DRS) demonstrated a narrowed optical band gap of 2.69 eV for the S2-TiO2/NiTiO3 composite, indicative of enhanced visible-light absorption. SEM imaging showed a sheet-like NiTiO3 framework decorated with spherical TiO2 nanoparticles ranging from 20 to 50 nm. The S2−TiO2/NiTiO3 sample exhibited a significantly higher surface area (65.215 m2/g) compared to S1-TiO2, correlating with its superior photocatalytic performance. Photocatalytic experiments conducted under natural sunlight using Eriochrome Black T (EBT) and Methyl Red (MR) as model azo dyes confirmed the enhanced activity of the S2-TiO2/NiTiO3 heterostructure. These results establish the S2-TiO2/NiTiO3 composite as a highly effective and environmentally sustainable photocatalyst for the remediation of dye-contaminated water.