Photocatalytic hydrogen production and sulfamerazine degradation via a novel dual S-scheme photocatalyst: Nanocomposite synthesis, characterization and mechanism insights

Creating highly effective photocatalysts is crucial for harnessing solar energy to degrade pollutants and produce hydrogen (H₂). In this study, we successfully synthesized a novel dual S-scheme iron oxide (Fe₂O₃)/bismuth oxide (Bi₂O₃)/titanium dioxide (TiO₂) ternary photocatalyst using a straightforward method. This photocatalyst was employed for efficient photocatalytic water splitting and the degradation of the antibiotic sulfamerazine (SMZ) under visible light. Various characterization and photoelectrochemical techniques, including scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), Brunauer–Emmett–Teller surface area analysis (BET), photocurrent measurements, Mott-Schottky analysis, photoluminescence (PL), electrochemical impedance spectroscopy (EIS), and electron spin resonance (ESR), were utilized to analyze the synthesized materials. Among the synthesized nanocomposites, the 15 wt% Fe₂O₃/Bi₂O₃/TiO₂ (15FeBi/TiO₂) composite demonstrated exceptional photocatalytic efficiency, achieving 98 % SMZ degradation and a hydrogen production rate of 590.36 μmol/g·h. Experimental results, including scavenging tests and ESR findings, highlighted the crucial role of hydroxyl radicals (•OH) and superoxide radicals (•O₂⁻) in the photocatalytic process. Moreover, liquid chromatography-mass spectrometry (LC-MS) results proposed three degradation pathways, and quantitative structure-activity relationship (QSAR) analysis showed that the toxicity of intermediates was effectively reduced. The 15FeBi/TiO₂ photocatalyst also exhibited excellent reusability, retaining about 85 % of its initial activity after five cycles, and proved effective against various pollutants and in real water matrices. This research contributes to the design and development of high-activity heterojunction photocatalysts for superior clean energy generation and pollutant degradation under visible light.