Evidence for a dual mechanism in the TiO2/CuxO photocatalyst during the degradation of sulfamethazine under solar or visible light: Critical issues

• Published in: Journal of photochemistry and photobiology. A, Chemistry. Chemistry., 2019-04, Vol.375, p.270-279
• Main Authors: Yu, Jiajie, Kiwi, John, Wang, Tianhe, Pulgarin, Cesar, Rtimi, Sami
• Format: Article
• Language: English
• Subjects: Anatase; Aqueous solutions; Catalysis; Charge transfer; High performance liquid chromatography; Indoor visible light; Interface stability; Interfacial charge transfer (IFCT); Irradiation; Kinetics; Light; Light irradiation; Liquid chromatography; Luminous intensity; Nanotechnology; Nanotubes; Oxidation; Photocatalysis; Photocatalysts; Photodegradation; Photoelectron spectroscopy; Photoelectrons; Reaction kinetics; Reactive oxygen species; Redox catalysis; Scanning electron microscopy; Semiconductor-oxide photocatalysis; Sulfamethazine; Surface plasmon resonance; Titanium dioxide; Transmission electron microscopy; X ray photoelectron spectroscopy; X-ray diffraction
• ISSN: 1010-6030; 1873-2666
• DOI: 10.1016/j.jphotochem.2019.02.033

[Display omitted] •Photocatalytic degradation of sulfamethazine on TiO2/CuxO nanotubes are investigated.•Sulfamethazine degradation was complete within 3 h in acid aqueous solution.•The photocatalyst was analyzed by scanning and transmission electron microscopy.•Interfacial charge transfer under solar light on the TiO2/CuxO surface is suggested.•Surface plasmon resonance mechanism is suggested under visible light. This study presents the photocatalytic degradation of sulfamethazine (SMT) on TiO2/CuxO nanotubes (NTs) by a differentiated mechanism under low intensity solar light and indoor visible light irradiation. In the presence of TiO2/CuxO nanotubes, the SMT-degradation was complete within 3 h (in acid aqueous solution). The surface of the photocatalyst used was registered by scanning and transmission electron microscopy SEM/TEM. By X-ray diffraction (XRD), the anatase and rutile phases were detected in the TiO2/CuxO(1%) materials. This photocatalyst led to the fastest SMT-degradation. By X-ray photoelectron spectroscopy (XPS) the TiO2 and CuxO species deconvoluted signals provided the evidence for the redox catalysis taking place during SMT-degradation. Cu2O was the major component in the TiO2/CuxO(1%) samples as detected by XPS. The SMT-degradation kinetics was monitored by high performance liquid chromatography (HPLC). The reactive oxidative species (ROS) generated by TiO2/CuxO surface under solar and visible light irradiation were unambiguously identified by appropriate scavengers. The band-gap of the TiO2/CuxO NTs prepared in this study is reported. The stability of the TiO2/CuxO leading to SMT-photodegradation was monitored. The interfacial charge transfer (IFCT) photo-activated by solar light on the TiO2/CuxO surface is suggested to proceed via a Schottky barrier. But under visible light a mechanism involving surface plasmon resonance (SPR) mechanism is suggested to account for the observed IFCT.