AV2O6 (A = Zn, Ca, Mg) and NaBH4 - Reduced AV2O6: A Comparative study of structural, optical, and photocatalytic insights for Methylene blue degradation

In this study, we present findings on the photocatalytic degradation of methylene blue (MB) by AV₂O₆ (A = Zn, Ca, Mg) and sodium borohydride reduced AV₂O₆ (A = Zn, Ca, Mg) under both visible light and sunlight. AV₂O₆ compounds were synthesized via a solid-state method, and their morphology, electronic structure, and optical properties were examined using various characterization techniques. The reduced form of AV₂O₆, referred to as R-AV₂O₆ (A = Zn, Ca, Mg), exhibits superior photocatalytic performance compared to the original AV₂O₆ materials, attributed to improved charge carrier separation. X-ray diffraction (XRD) analysis confirmed the formation of a single-phase structure for all AV₂O₆ materials. Field emission scanning electron microscopy (FESEM) revealed particle sizes in the range of 2.5–2.8 μm, 1.1–1.4 μm, and 0.8–1.1 μm for ZnV₂O₆, CaV₂O₆, and MgV₂O₆, respectively. Analysis via UV–Vis DRS explained that the bandgap values for AV₂O₆ varied between 2.15 and 2.64 eV and for R-AV₂O₆ varied between 1.78 and 2.52 eV. R-AV₂O₆ (A = Zn, Ca, Mg) phases demonstrate a significantly higher degradation rate of MB compared to the individual AV₂O₆ components. Potential degradation pathways for MB were proposed based on high-resolution mass spectrometry (HRMS) analysis. Importantly, this research marks the first report on the photocatalytic application of MgV₂O₆ and reduced AV₂O₆ (A = Zn, Ca, Mg) materials for MB degradation, establishing a new class of efficient visible and sunlight active photocatalysts.