Photoelectrocatalytic degradation of methylene blue using F doped TiO₂ photoelectrode under visible light irradiation

Photoelectrocatalysis (PEC) has attracted great interest due to cost effectiveness and high efficiency in water treatment. In this study, F doped TiO₂ (F-TiO₂) photoelectrodes with honeycomb like morphology were prepared, and the PEC performance was investigated. F-TiO₂ particles that showed enhanced absorption of visible light were synthesized via a sol-gel method. F-TiO₂ particles were anchored onto the surface of F-doped SnO₂ glass by a screen-printing method to prepare the F-TiO₂ photoelectrodes. The PEC performance of the F-TiO₂ photoelectrodes was investigated via the degradation of methylene blue (MB) under visible light irradiation. The results show that the F-TiO₂ photoelectrodes exhibited an excellent PEC performance that was affected by the F doping content, applied bias and solution pH. A maximum decolorization percentage of 97.8% was achieved by the FT-15 photoelectrode, with a 1.4 V bias at pH 9.94 after 4.0 h of visible light irradiation. The high PEC performance of the F-TiO₂ photoelectrodes is mainly ascribed to the efficient separation of electron-hole (e⁻-h⁺) pairs and the creation of active radicals such as hydroxyl radicals ([rad]OH). The PEC decolorization kinetic data were analyzed using the first-order kinetic model and the Langmuir-Hinshelwood (L-H) model. The data indicates that the PEC degradation of MB molecules mainly occurred on the surface of the F-TiO₂ photoelectrodes, and the MB molecules were discolored mainly by h⁺ (41.5%) and [rad]OH (46.5%). In addition, 8.2% of the MB molecules were discolored by other oxidative species, and 3.8% of the MB molecules were discolored by self-sensitized oxidation.