Mesoporous amorphous tungsten oxide electrochromic films: a Raman analysis of their good switching behavior

Abstract

A c c e p t e d M a n u s c r i p tThe intercalation and de-intercalation of lithium cations in electrochromic tungsten oxide thin films are significantly influenced by their structural and surface characteristics.In this study, we prepared two types of amorphous films via the sol-gel technique: one dense and one mesoporous in order to compare their response upon lithium intercalation and deintercalation.According to chronoamperometric measurements, Li + intercalates/de-intercalates faster in the mesoporous film (24s/6s) than in the dense film (48s/10s bronze.

Ion intercalation dynamics of electrosynthesized mesoporous WO3 thin films studied by multi-scale coupled electrogravimetric methods

“…21,50 The aspect of crystallinity of the films can also be studied when WO 3 thin films thermally treated at different temperatures, thus possessing different degree of crystallinity. The fact that crystalline materials increase the energy barrier for lithium ions, and thus their electrochemical capacity may be inferior than their amorphous analogues has been discussed in the literature.…”

“…7,20,21 This reversible electrochemical insertion or intercalation of electrolyte ions into an electrode material is the fundamental operation principle of many electrochemical devices; therefore it is crucial to optimize the interactions between electrolyte ions and electrode materials. 7,20,21 This reversible electrochemical insertion or intercalation of electrolyte ions into an electrode material is the fundamental operation principle of many electrochemical devices; therefore it is crucial to optimize the interactions between electrolyte ions and electrode materials.…”

“…[2][3][4][20][21][22] Various synthesis methods such as sol-gel, 2,3,20 spray pyrolysis/sputtering, 23,24 and hydrothermal synthesis, 25,26 are commonly employed for the elaboration of WO 3 leading to different morphologies. [2][3][4][20][21][22] Various synthesis methods such as sol-gel, 2,3,20 spray pyrolysis/sputtering, 23,24 and hydrothermal synthesis, 25,26 are commonly employed for the elaboration of WO 3 leading to different morphologies.…”

“…6,[27][28][29][30] The incorporation of surfactant molecules in the electrogenerated film results in the production of thin nanostructured films by using potential-controlled self-assembly of surfactant-inorganic aggregates at solid-liquid interfaces. The morphology dependent performance and ion intercalation behaviour of electrochromic WO 3 thin films have been investigated by several in situ or ex situ characterization techniques, [31][32][33][34][35] including electrochemical and optical methods, 5,20,22 wide-angle X-ray scattering combined with electrochemical studies, 20 Raman spectroscopy, 21 and X-ray photoelectron spectroscopy studying electrochromic materials before and after cation intercalation. After deposition, surfactants can be easily removed from the pores by washing with a suitable alcohol, leading to the porous inorganic replicas of the surfactant phases.…”

“…The ac-electrogravimetry simultaneously measures the electrochemical impedance, DE/DI(o), and the mass/potential transfer functions (Dm/DE(o)) during a sinusoidal potential perturbation with a small amplitude applied to the modified electrode. 5,21,50 Here, we particularly focus on the amorphous materials rather than crystalline ones to emphasize its role in the electrochemical performance of WO 3 films. It provides the access to the relevant information on (i) the kinetics of species transferred at the solid/ solution interfaces, and their transport in the bulk of the materials, (ii) the nature of these species as well as their relative concentration within the material.…”