Electrochromic Behavior of Molybdenum Trioxide Thin Films, Prepared by Thermal Oxidation of Electrodeposited Molybdenum Trisulfide, in Mixtures of Nonaqueous and Aqueous Electrolytes

Abstract

Electrochromic molybdenum trioxide thin films were prepared by thermal oxidation in air of electrodeposited molybdenum trisulfide. MoO, prepared at temperatures ranging from 400 to 550°C were found to be polycrystalline. The best electrochromic properties (coloration efficiency and coloration time) evaluated in 1 M LiClO4/propylene carbonate were observed for films prepared by annealing at 425°C for 10 mm. The coloration efficiency (35 cm'/C) for these optimum films compare well with those reported in the literature. The intensity of coloration of the film (absorbance at 634 nm) was found to scale linearly with film thickness. The electrochemical reduction of MoO, involves the transformation of Mo6 species to Mo', evidenced by x-ray photoelectron spectroscopy. The stability of molybdenum trioxide-coated tin oxide electrodes upon cycling and switching between oxidized and reduced states was investigated by cyclic voltammetry potential-step experiments, and in situ spectroelectrochemistry. The results indicate that the stability of the molybdenum trioxide electrode is improved when it is used in a 0.1 M LiClO4, 14 mM HC104, 2% 11,0/PC solution rather than in a pure, nonaqueous electrolyte such as 0.1 M LiC1O4/PC. The improved stability is related to the fact that the chemical disorder induced by cycling the MoO, electrode in the protic media is much less severe than in the aprotic media, primarily because while Li are intercalated in the latter, only protons are intercalated in the aqueous/nonaqueous mixture.

Effect of Ablation Rate on the Microstructure and Electrochromic Properties of Pulsed-Laser-Deposited Molybdenum Oxide Thin Films

“…In a real-time device, the electrochromic metal oxide is coated as a thin film over a suitable (often transparent) substrate. The deposition method strongly affects the adhesion, occurrence, and variations of the photo/electro-optic effect in the films. , It also alters the morphology, leading to a change in impedance, the diffusion of intercalating species, and electrode reaction kinetics. Different film growth techniques are currently used for molybdenum oxide thin film deposition such as electron beam evaporation , sputtering, chemical vapor deposition (CVD), and electrodeposition. − …”

Electrochemical Preparation of Molybdenum Trioxide Thin Films: Effect of Sintering on Electrochromic and Electroinsertion Properties

“…However, we have observed that postdeposition heat treatment of these films at relatively low temperatures (e450 °C) markedly influences the overall electroinsertion properties (insertion kinetics and charge storage capacity). While others [23][24][25] have briefly discussed the influence of sintering temperature on structural features and electroinsertion properties of electrodeposited MoO 3 thin films, to our knowledge no detailed investigations concerning the effect of film microstructure, metal oxidation state, and water content on the electrochromic and ion storage behavior have been reported.…”

Molybdenum oxide (MoO3) thin film based electrochromic cell characterisation in 0·1M LiClO4.PC electrolyte

“…where Q in (mC cm 22 ) is the charge injected during the colouration cycle. The Q in was calculated by integrating the current density of the colouration cycle between the starting and ending time of each period according to the following equation…”