CeO₂-based nanoheterostructures with p–n and n–n heterojunction arrangements for enhancing the solar-driven photodegradation of rhodamine 6G dye

Recently, great attention has been directed towards the fabrication of solar-driven nanophotocatalysts for wastewater treatment. Thus, in this work, CeO₂-based nanoheterostructures were synthesized by mixing n-type CeO₂ nanoparticles (NPs) with p-type Cu₂S and n-type Ag₂S NPs to form Cu₂S/CeO₂ (p–n) and Ag₂S/CeO₂ (n–n) nanoheterostructures, respectively. The synthesis of pristine CeO₂ and CeO₂-based nanoheterostructure architectures and their characterization is conducted using XRD, XPS, TEM, HRTEM, UV–Vis, N₂ sorpometry, and electrochemical techniques. Pristine CeO₂ NPs had a particle size of 3.9 nm and a surface area of 72.40 m² g⁻¹, which increased with the generation of nanoheterostructures to 12.3 and 11.1 nm and to 81.5 and 101.16 m² g⁻¹ for Cu₂S/CeO₂ and Ag₂S/CeO_2, respectively. Moreover, both nanoheterostructures showed strong levels of visible light absorbance relative to UV absorber pristine CeO₂ NPs. Moreover, Mott-Schottky measurements were collected to determine electrochemical flat potential and band gap structures, and based on the derived results, a schematic diagram of the separation of electron–hole and insight into mechanistic routes involved are given. The photocatalytic degradation of rhodamine 6G (R6G) under natural sunlight was investigated. Based on changes in the temporal UV–Vis spectra of R6G observed over time, photocatalytic efficiencies were estimated at 23%, 44% and 30% for pristine CeO₂, Cu₂S/CeO₂ and Ag₂S/CeO₂, respectively. The enhancement of the photocatalytic performance of the nanoheterostructures was attributed to the generation of p–n and n–n heterojunction arrangements, which facilitated photogenerated charge separation and transfer.