Interfacial coupling perovskite CeFeO₃ on layered graphitic carbon nitride as a multifunctional Z-scheme photocatalyst for boosting nitrogen fixation and organic pollutants demineralization

The application of pristine graphitic carbon nitride (PCN, g-C₃N₄)/cerium ferrite (CeFeO₃, CFO) composites as photocatalysts for energy production and water treatment has not yet been reported despite its great potential. In this study, CFO, an orthorhombic perovskite-type oxide, was covalently coupled to PCN via a facile single-step calcination strategy. Compared to PCN, optimized 1% CFO-doped PCN (PCN@CFO₁) exhibited wide ranges of organic-micropollutant removal (sulfamethoxazole (SMX), atrazine, and bisphenol A) and achieved approximately 49.9% of total-organic-carbon (TOC) removal for SMX in 4 h with 5 stable reusable performances. Further, scavenger experiments and the electron paramagnetic resonance (EPR) spin-trap analysis revealed that PCN@CFO₁ could produce superoxide (O₂^−[rad]) and hydroxyl radicals ([rad]OH) for organic-pollutant degradation. Meanwhile, the intermediate species of organic pollutants were investigated using liquid chromatography-tandem mass spectrometry to identify the degradation pathways. Of note, PCN@CFO₁ achieved up to 573.12 µmol l⁻¹ g⁻¹ of ammonia production rate and 2.92% of apparent quantum efficiency of nitrogen photo-fixation at 400 nm, which was 8 times higher than that of PCN. Through coupling CFO and PCN, the flat band potential was found to be upshifted, and a high ratio of the Ce³⁺ interface associated with oxygen vacancies was generated, resulting in the formation of a Z-scheme system. Remarkably, the formation of the Z-scheme structure on PCN@CFO₁ showed enhancement in charge transfer, hydrophilicity, and charge separation, significantly improving the photocatalytic performance for organic-micropollutant demineralization and nitrogen photo-fixation under UVA-LED (400 nm) light irradiation. Our study provided a facile and scalable preparation strategy for multifunctional photocatalysts that could be effectively activated under energy-efficient UVA-LED irradiation for energy production and emerging pollutants degradation.