ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

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

N. Padmavathy, M. Vinuth, M. Madhukara Naik, H. J. Yashwanth, and K. H. Hemakumar

Department of Chemistry, Cambridge Institute of Technology, Bangalore, India

E-mail: drkhhemakumar@gmail.com

Received: 6 November 2025  Accepted: 24 March 2026

Abstract:

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.

Keywords: TiO2; TiO2/NiTiO3 Nanocomposites; microwave combustion; photocatalytic; Azo dyes; Eriochrome Black T; Methyl Red

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-026-04843-0

Chemical Papers 80 (7) 7665–7678 (2026)