Modulating photocatalytic activity of nitrogen doped TiO2 nanoparticles via magnetic field

• Published in: Journal of environmental chemical engineering 2024-10, Vol.12 (5), p.113643, Article 113643
• Main Authors: Gómez-Polo, Cristina, Cervera-Gabalda, Laura, Garaio, Eneko, Beato-López, Juan Jesús, Peréz-Landazábal, José Ignacio
• Format: Article
• Language: English
• Subjects: Magnetic field; Nanoparticles; Photocatalysis; TiO2
• ISSN: 2213-3437
• DOI: 10.1016/j.jece.2024.113643

The effect of the magnetic field on the photocatalytic activity of TiO2-based nanoparticles is analyzed using a magnetically-assisted photoreactor with permanent magnets to generate a controlled uniform magnetic field, B (≈ 82 mT). Nitrogen doped TiO2 nanoparticles (sizes around 10 nm) were synthesized through a solvothermal method employing Ti(IV) butoxide and HNO3 (x = 0, 0.5, 1, 1.5 and 2 mL) as precursors and their structural, optical and magnetic properties were analyzed. Specifically, nitrogen doping is confirmed through Hard X-ray Photoelectron Spectroscopy (HAXPES) in those samples synthesized with low HNO3 concentrations (x = 0.5, 1). The correlation between spin polarization (magnetic susceptibility) and visible photocatalytic activity (methyl orange as a model organic pollutant) is particularly analyzed. Surprisingly, opposite effects of the magnetic field on the photocatalytic performance are found in the visible range (above 400 nm) or under UV-Vis irradiation (decrease and increase in the photocatalytic activity, respectively, under magnetic field). The Langmuir-Hinshelwood model allows us to conclude that the strong decrease in adsorption under the magnetic field (around 42 % for x = 0.5) masks the increase in the kinetic constant (close to 58 % for x = 0.5) related mainly to the effect of Lorentz forces on the reduction of the electron-hole recombination. [Display omitted] •Nitrogen-TiO2 nanoparticles as visible photocatalysts under magnetic field effects.•Hard X-Ray Photoelectron Spectroscopy confirms nitrogen doping of anatase TiO2.•Visible photocatalytic performance is related to higher magnetic susceptibility values.•Decreased absorption under magnetic field is checked through Langmuir–Hinshelwood kinetic model.•Uniform magnetic field accelerates the kinetics of the photocatalytic phenomena (methyl orange degradation).