Photoelectrochemical Performance of S,N-Codoped TiO₂ Films Supported on Ti and their Enhanced Photoelectrocatalytic Activity in the Generation of Hydroxyl Radicals

Abstract

New photoanodes for recalcitrant pollutant degradation should harvest photons from a wide region of the solar spectrum and promote a direct water oxidation reaction towards the hydroxyl radical generation. For this purpose, sulfur, nitrogen-codoped titanium dioxide (S,N-TiO2) films were prepared with different sulfur percentages (1.0, 2.5 and 5.0 at.%) on Ti expanded meshes by sol-gel dip-coating followed by thermal treatment at 400 °C. The morphology, composition, oxidation states of dopants, structural features, optical and semiconducting properties of S,N-TiO2 were used for the materials characterization. While sulfur was found as S4+ or S6+ cations related to surface doping, nitrogen appears as N3− anion occupying substitutional positions in TiO2. This caused an improvement in the photoelectrochemical response of TiO2 related to a decrease of up to 0.25 eV in the optical band gap and the alignments of the TiO2 band structure. S,N-TiO2 films exhibit significantly higher photoelectrocatalytic activity towards ·OH generation under UV–vis light irradiation than the undoped TiO2 films. Using 2.5 at.% S,N-TiO2 film, an increase of 166% in current efficiency was obtained at 0.5 V vs Ag/AgCl, in regard to undoped TiO2 films, together with an enhance of 8.8 times in the initial ·OH generation rate.

Hurdles and recent developments for CdS and chalcogenide‐based electrode in “Solar electro catalytic” hydrogen generation: A review

“…Most extensively studied among them is TiO 2 , which has large band gap of 3.2 eV and absorbs only UV radiation. [23,24] ZnO having similar short comings is also a material of great interest in PEC research. Although its properties are similar to TiO 2 but it is less efficient in terms of PEC performance.…”

Kinetic Approach by Photocurrent Measurements to the Photoelectrocatalytic Oxidation of an Anionic Surfactant Using an S,N-TiO2/Ti Electrode: Distinguishing Between Direct and Indirect Mechanisms

“…Sols were prepared by using a 1.0:4.6 alkoxide: alcohol volume ratio, a 1.0:1.1 alkoxide: acetylacetone molar ratio and a 1.0:4.0 alkoxide: water molar ratio. Thiourea and urea was added to prepare S,N-TiO 2 films with a sulfur percentage of 2.5 at.%, this atomic percentage were selected according to previous work, in which the crystalline, optical and semiconductor properties as well as photoelectrochemical performance displayed for 2.5 at.% S,N TiO 2 /Ti electrode [29]. Ti support was dip-coated with four layers of sol at 6 cm•min −1 immersion rate.…”

“…Ti support was dip-coated with four layers of sol at 6 cm•min −1 immersion rate. The films were dried at 100 °C for 1 h and then annealed at 400 °C for 1 h [29].…”