Optimizing interfacial band alignment and charge transfer in CuO/g-C3N4/InVO4 ternary heterojunction nanostructures

The current research explores the development of advanced nanocomposite materials featuring nanostructured heterojunctions with optimized capabilities for efficient photogenerated charge-carrier separation and generation of reactive species under solar-light excitation. This work introduces a novel ternary heterojunction, CuO/g-C₃N₄/InVO₄, synthesized through a combined impregnation–hydrothermal method. The as-prepared nanoheterostructures were comprehensively characterized to understand their structural, textural, optical, and electrochemical properties, using a range of analytical techniques. The synergistic interactions among pure CuO, InVO₄, and g-C₃N₄, with particle sizes ranging from 5 to 56 nm, led to the formation of the CuO/g-C₃N₄/InVO₄ heterojunction, which was confirmed through X-ray photoelectron spectroscopy (XPS) analysis. To further understand the electronic structure, a band alignment diagram of the n-type CuO, InVO₄, and g-C₃N₄ semiconductors was established based on data obtained from XPS and UV–vis diffuse reflectance spectroscopy (DRS/UV–vis). Additionally, a photoluminescence (PL)-based hydroxyl radical (•OH) trapping test was carried out on each individual compound, as well as their binary combinations, to assess charge-transfer behavior at the interfaces of the ternary heterojunction. The CuO/g-C₃N₄/InVO₄ heterojunction was ultimately rationalized, and its type was elucidated through hydroxyl radical trapping experiments and a constructed band alignment diagram.