Thermodynamic Study of Mehtylene Blue Adsorption and Photocatalytic Degradation on The N‐Doped TiO ₂ Thin Films: A DFT and Experimental Study

Abstract N‐Doped TiO 2 coatings (N‐TiO 2 ) were synthesized and characterized. The effect of the doping process on the physical‐chemical properties and photocatalytic efficiency of Methylene Blue (MB) under visible light irradiation were studied. The bare TiO 2 showed only anatase crystalline structure. Furthermore, after the doping process, a slight transition from anatase to rutile was verified. The HRXPS confirmed that the doping process was effective. The N 2 sorption using the BET assay showed a slight increase in surface area after the doping process. MB adsorption kinetic showed also a slight increase for doped TiO 2 films, showing as best fitting the Langmuir model. Furthermore, a modification on the electronic structure was observed, showed by the modification of the optical absorption profile in the doped material. The results showed that the MB adsorption on N‐TiO 2 thin films was endothermic (▵H=11 kJ mol −1 ) and a spontaneous process (▵G=−6.45 kJ mol −1 ). We performed DFT calculations to three simulated doped‐structures. The Gap value, the global reactivity indexes and, the Fukui function isosurfaces are presented. Finally, the scavenger tests suggested that and OH⋅ could be the main ROS driving the photocatalytic process.