Electrochemical properties of thin films of V2O5 doped with TiO2. (August 2018)

• Record Type: Journal Article
• Authors: Moura, E.A.; Cholant, C.M.; Balboni, R.D.C.; Westphal, T.M.; Lemos, R.M.J.; Azevedo, C.F.; Gündel, A.; Flores, W.H.; Gomez, J.A.; Ely, F.; Pawlicka, A.; Avellaneda, C.O.
• Is Part Of: Journal of physics and chemistry of solids. Volume 119(2018)
• Page Start: 1
• Page End: 8
• Publication Date: 2018-08
• Subjects: Sol-gel process -- Dip coating -- Thin film V2O5:TiO2 -- Diffusion equation; Solids -- Periodicals; Solides -- Périodiques; Solids; Periodicals; 530.41
• DOI: 10.1016/j.jpcs.2018.03.023
• Languages: English
• ISSNs: 0022-3697

Abstract

Abstract: The paper presents a systematic study of the electrochromic properties of thin films of V2 O5 :TiO2 for a possible utilization as counter-electrode in electrochromic devices. The V2 O5 :TiO2 thin films were prepared by the sol-gel process and deposited on a substrate of fluorine-tin oxide transparent electrode (FTO) using the dip coating technique and heat treatment at 350 °C for 30 min. The films were characterized by chronocoulometry, cyclic voltammetry (CV), UV-Vis, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), atomic force microscopy (AFM), profilometry, and X-ray diffraction (XRD). The best results were obtained for the film of V2 O5 with 7.5 mol% of TiO2, which presented highest ion storage capacity of ∼106 mC cm −2 and redox reversibility of 1. The diffusion of the Li + ions into the thin films was modeled by solving Fick equations with appropriate boundary conditions for a plane sheet geometry. Besides that, these films showed optical modulation of 35% at 633 nm after coloration and bleaching. The XRD patterns revealed that the films have an orthorhombic crystal structure; the AFM and the profilometry confirmed roughness and thickness of 16.76 and 617 nm, respectively. Graphical abstract: Highlights: V2 O5 :TiO2 sol-gel thin films were synthesized and compared to V2 O5 thin films. The best value of charge density of ∼106 mC/cm 2 was obtained for V2 O5 :TiO2 7.5 mol%. UV-Vis of V2 O5 :TiO2 showed ΔT = 41% at 633 nm between colored and bleached states. V2 O5 orthorhombic crystalline structure is dispersed in amorphous phase of TiO2 . SEM and AFM pictures reveal a regular and homogeneous surface of films.