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Effect of the Magnetostriction Induced on the Crystalline Structure of Nanoparticulate TiO 2 Films Supported on Stainless Steel Mesh Electrodes and Their Relationship with the Photocatalytic Decoloration of Aqueous Orange G Solutions

2023; Institute of Physics; Volume: MA2023-02; Issue: 54 Linguagem: Inglês

10.1149/ma2023-02542571mtgabs

2152-8365

Jesus Israel Valdez Nava, Erika Bustos, Laura Lupita Martinez Rodriguez, Fabricio Espejel‐Ayala, S. Sepúlveda-Guzmán, J. Manríquez,

Water Quality Monitoring and Analysis

The study of ferromagnetism (FM) in non-cubic semiconductor oxides such as defective TiO 2 is attractive due to their applications in photocatalysis [1]. FM can be activated in TiO 2 nanomaterials by promoting oxygen vacancies (V O ) located in paramagnetic defected sites Ti 3+ V O Ti 4+ . In this context, the V O can induce in Ti 3+ -doped TiO 2 structures remarkable magnetic anisotropy energy (MAE) of 6.51x10 6 erg/cm 3 , thus indicating the magnetic saturation should be achieved at magnetic fields (MFs) of ~425 gauss [2,3]. Therefore, magnetostriction can be observed in ferromagnetic TiO 2 films as a phenomenon in which their dimensions and shapes are changed when they are magnetized. In this work, stainless steel mesh electrodes (ss) were modified by nanoparticulate TiO 2 films (ssTiO 2 ) enriched by Ti 3+ V O Ti 4+ sites, to gain an understanding of the effects of magnetostriction on the photocatalytic properties of ferromagnetic TiO 2 electrodes. In this way, MFs having intensities ( H ) of 125, 250, 500, 1000, and 2000 gauss were applied to the ssTiO 2 electrodes for 80 min under UV light illumination for increasing the number of Ti 3+ V O Ti 4+ sites. Our results revealed that the magnetic lines promoted compression of the TiO 2 structure when achieving pressures p >4.67 GPa for H >425 gauss in p =1/2(MAE/4p gauss 2 ) H 2 . Consequently, the degree of disorder (0<b<1) of the electron traps at the intra-bandgap state's distribution along the thickness-axis(i.e. the x -axis) of TiO 2 films decreased significantly because the fraction of trapped electrons f trap ( x ) at the quasi-Fermi level E F ( x ) was maximized according to f trap ( x )= m [ e m (E F ( x )-E F (0)) -1], where m = k T/b ( k and T are the Boltzmann constant and the absolute temperature) [4,5]. Later, it was observed a significant increase of trapped holes able to carry out the direct photocatalytic oxidation of aqueous orange G (without electron scavenger’s assistance, e.g. gaseous O 2 ). On the other hand, the photogeneration of oxidant •OH radicals decreased dramatically while H increased [6]. [1] Y. Bian et al., RCS Adv., 11 (2021)6284.; [2] D. Kim et al., J. Phys.: Condens. Matter , 21 (2009)195405.; [3] B. Shao et al., J. Appl. Phys. , 115 (2014)17A915. [4] N. Kopidakis et al., J. Phys. Chem. B , 107 (2003)11307. [5] J. van de Lagemaat et al., J. Phys. Chem. B , 104 (2000)4292. [6] K.-I Ishibashi et al., J.Photochem.Photobiol.A , 134 (2000)139-142. Acknowledgements The authors thank the National Council for Science and Technology (CONACyT) Mexico for the funding support (grants CB No. 258789 and FOINS No. 3838). JIVN thanks CONACyT for his doctoral fellowship support (grant No. 893260).