Understanding the Role of Morphology in the Visible-Light-Driven Sulfamethoxazole Degradation by Ag ₂ SeO ₃ -Based Photocatalysts Synthesized in Different Solvent Media: An Experimental–Theoretical Approach

The present research examines the photodegradation of sulfamethoxazole under visible light using Ag₂SeO₃ (ASO), synthesized via a sonochemical route in three different reaction environments: aqueous (ASOwat), ammoniacal (ASOamm), and ethanolic (ASOet) . X-ray diffraction, Raman, UV-visible, and photoluminescence spectroscopy measurements were carried out to further understand the structural changes driven by the synthesis̀ medium and their contribution to the photocatalysis. Additionally, field emission scanning electron microscopy revealed significant morphological differences among the samples, which were further confirmed by surface-energy calculations based on density functional theory associated with Wulff constructions. Our results indicate that surface-dependent band gap variations, influenced by the specific surface energy of the exposed facets, may assist in enabling partial visible-light activation, even though bulk ASO exhibits a larger band gap (<i>E</i>_gap ∼ 3.70 eV). The ASOet sample showed the highest performance (∼55% sulfamethoxazole degradation and 54% TOC mineralization) within 120 min. Thus, our work further reinforces the critical importance of particle morphology, which supersedes the overall band gap energy of the material, making visible-light excitation possible even for larger band gap materials.