Unraveling the structural and optical properties of WO3/anatase–brookite TiO2 heterostructures for enhanced visible-light photocatalysis

Abstract

Titanium dioxide (TiO2) is a leading semiconductor photocatalyst for environmental remediation, valued for its chemical stability, polymorphic phases, and tunable optoelectronics. Its wide band gap (approximately 3.0–3.2 eV), however, limits visible-light activity, necessitating electronic structure engineering via phase modification. The present study explores the effect of tungsten loadings (2.5, 5.0 and 10.0 wt%) on biphasic anatase–brookite TiO2 via the synthesis of WO3–TiO2 heterostructures using a modified sol–gel method. The study aimed at providing insights into the relationship between tungsten concentration, interfacial structural properties, and resulting photocatalytic efficiency. X-ray diffraction (XRD) analysis revealed that modification induced the formation of a distinct secondary WO3 phase alongside the anatase–brookite TiO2, establishing a multi-phase junction that was most pronounced at 10.0 wt% loading. The 2.5 wt% WO3–TiO2 heterostructures exhibited the narrowest optical bandgap (2.46 eV), a favorable pore diameter of 33.62 nm, and a high pore volume of 0.265 cm3 g−1 . Photoluminescence spectroscopy showed the strongest emission quenching for 2.5 wt% WO3–TiO2, indicating reduced charge-carrier recombination and improved heterojunction-assisted charge separation. This composition delivered the highest photocatalytic performance, degrading 91.5% of methylene blue under visible light within 60 min, compared with 28.87% for pristine TiO2. These WO3/anatase–brookite TiO2 heterostructures, therefore, represent efficient, robust photocatalysts for textile wastewater treatment.