High-purity indium vanadate (InVO₄) and graphitic carbon nitride (g-C₃N₄) were successfully synthesized and thoroughly characterized to investigate their optoelectronic properties and interfacial charge transfer behavior. X-ray diffraction (XRD) analysis confirmed the phase purity and crystallinity of the individual materials. UV–vis diffuse reflectance spectroscopy revealed direct band gaps of 2.48 eV for InVO₄ and 2.99 eV for g-C₃N₄, highlighting their suitability for visible-light-driven applications. X-ray photoelectron spectroscopy (XPS) provided detailed insight into the surface composition and valence band positions. Furthermore, Mott–Schottky measurements indicated that both materials exhibit n-type semiconducting behavior and allowed the determination of their conduction band edge potentials. The Fermi levels were estimated using valence band maximum (VBM) analysis, and the overall band alignment revealed a staggered (Type II) configuration at the interface.

To probe the charge carrier dynamics, steady-state photoluminescence (PL) spectroscopy was employed, specifically targeting the generation of hydroxyl (•OH) radicals under illumination. The enhanced production of these reactive oxygen species provided strong evidence for a direct Z-scheme charge transfer mechanism between InVO₄ and g-C₃N₄. This mechanism promotes effective charge separation and preserves strong redox potentials, making the heterostructure a promising candidate for photocatalytic applications such as pollutant degradation and hydrogen evolution. These findings offer valuable insights into band structure tuning and heterojunction design strategies.