CeMnO3 Nanoparticle-Decorated g-C3N4 Nanosheets as Z-Scheme Heterostructures for Efficient Photocatalytic Degradation of Dyes

The design of efficient photocatalysts for dye degradation is a challenging task for the scientific community. Semiconductor-based photocatalysts such as g-C3N4 and oxides, utilizing solar energy, have been proven to be effective and promising approaches to resolve this issue to some extent. Constructing Z-scheme heterostructures by coupling g-C3N4 with suitable oxide semiconductors has shown substantial enhancement of the photocatalytic performance. In this article, perovskite-type CeMnO3 (5, 15, 25%) nanoparticle-decorated g-C3N4 nanosheets are fabricated as heterostructures, using a hydrothermal synthesis process, for efficient photocatalysis of organic dyes. The formations of heterostructures are confirmed through structural, microstructural, and elemental state analysis. Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) characterization techniques exhibited enhanced surface area and pore sizes, respectively. Ultraviolet-visible (UV-vis) diffuse reflectance spectroscopy (DRS), Mott-Schottky, and linear sweep voltammetry (LSV) analyses along with density functional theory (DFT) calculations predicted a p-n junction heterostructure. Electron paramagnetic resonance (EPR) studies revealed a broad spectrum with sextet hyperfine lines corresponding to Mn4+ and Mn2+ ions and enhanced intensity as compared to the parent ones, signifying the creation of oxygen vacancies in the heterostructure. The CeMnO3 (25 wt %)/g-C3N4 heterostructure showed highly efficient photocatalytic degradation of methylene blue under direct sunlight irradiation, with up to 99% degradation achieved in 120 min and excellent recyclability. The robustness of this photocatalyst was tested by adopting a similar process for methylene orange dye degradation, exhibiting 94% yield in 120 min. A tentative degradation mechanism is proposed based on the enhanced photodegradation efficiency and results obtained from electrochemical impedance (EIS), photoluminescence (PL), LSV, and first principal studies, which provides more insights into the photogenerated charge separation, enhanced photocurrent, and interfacial transfer efficiency through the Z-scheme charge transfer process. This study offers opportunities for designing high-performance Z-scheme hybrid photocatalysts for environmental remediation.