Electrochromic, electrochromism electrode

Baioni AP, Vidotti M, Fiorito PA, Ponzio EA, Cordoba de Torresi SI (2007) Synthesis and characterization of copper hexacyanoferrate nanoparticles for building up long-term stability electrochromic electrodes. Langmuir 23(12) 6796-6800... 

The LB technique is amenable to the fabrication of ECDs as demonstrated by the report of a thin-film display based on bis(phthalocyaninato)praseodymium(III).75 The electrochromic electrode in the display was fabricated by deposition of multilayers (10-20 layers, r+00-200 A) of the complex onto ITO-coated glass (7 x4cm2) slides. The display exhibited blue-green-yellow-red polyelectrochromicity over a potential range of —2 to +2V. After 105 cycles no significant... 

ECDs operate in the diffuse reflectance mode and the basic requirements for their functionality are (i) a primary electrochromic electrode (e.g. a polymer electrode) deposited on a substrate which is both optically transparent and electrically conducting (generally indium-tin-oxide(ITO)-... 

A promising EW may be obtained by combining tungsten trioxide, WO3, a well-known primary electrochromic electrode, which is coloured by the following lithium insertion-deinsertion process ... 

The ditetrazolium salts (309) have been patented for use in electrochromic electrodes which are used in display devices <89JAP01230026) and tetrazolium salts have also been developed for cell bioassays for neurotoxins active on voltage-sensitive sodium channels <93MI 417-03). Tests for inhibition of corrosion of zinc and brass carried out on 5-aminotetrazole showed it to be ineffective relative to other azoles <86MI 417-01). A number of tetrazoles including the 5-amino, 5-methyl, and 5-phenyl derivatives have been separately incorporated into surfactants used for corrosion inhibition with copper in water <9lMl4l7-07). Photopolymerizable resin compositions which are highly resistant... 

Ma, L., Li, Y, Yu, X., Zhu, N., Yang, Q., and Noh, C.-H. 2008. Electrochemical preparation of PMeT/TiO2 nanocomposite electrochromic electrodes with enhanced long-term stability. Journal of Solid State Electrochemistry 12, 1503-1509. 

Mobility of H-atoms in hydrogen oxide bronzes and related systems has excited considerable interest in view of their possible applications in e.g. catalysis and electrochromic electrodes for display devices. In practical materials the structure of the host oxide may be ill-defined and intercrystallite regions may contribute significantly to observed (bulk) mobilities. This article aims to present a consistent picture (derived from the published work of many scientists internationally) of the atomic level phenomena responsible for intracrystallite H-atom mobility in well-characterized single phases. The detailed characterization of such phases is discussed by Dickens Chippindale (Chapter 7). 

The electrochromic electrode of these devices, which can work either in the reflective or transmissive mode, is constituted by a conductive, transparent glass coated with electrochromic material. The counterelectrode can be of any material that provides a reversible electrochemical reaction in devices operating in the reflective mode (like electrochromic displays) by contrast, in variable light transmission electrochromic devices (like electrochromic windows) it has to be either colourless in both oxidized and reduced states or electrochromic in a complementary mode to the... 

Polymer-based, variable light transmission electrochromic devices have been fabricated with counter-electrodes that are either optically passive or electrochromic in the complementary mode. Two devices with pMeT, electrochemically grown by monomer oxidation on ITO-coated glass as the electrochromic electrode, having colourless counter-electrodes in both oxidized and reduced states, and operating in liquid electrolyte, such as PC-LiC104, have been developed [29, 30]. 

The device by Corradini et al uses an ITO counter-electrode at which occurs, without significant colour change, an electrochemical process that is presumably due to lithium ion insertion and involves up to ca. 7.5mCcm [29]. Figure 7.7 shows the transmittance in the visible and IR regions of the electrochromic-electrode in the undoped and doped states as well as of the ITO counter-electrode before and after lithium insertion. 

Both devices (2 cm x 1 cm) were assembled by facing at 2 mm distance a pMeT/ITO electrode (with polymer film in the undoped state) with the respective counter-electrode the devices operate by potential switches from —0.3 to 2.5 V and from 0 to 2.8 V (with respect to the electrochromic electrode), respectively. The overall electrochemical processes are as follows ... 

The colour change is from purple to transparent pale blue for both devices. Light modulation in devices with a colourless optically passive counterelectrode is governed solely by changes in the electrochromic electrode. 

The most convenient (and thus the most common) configuration of an electrochromic electrode is in the form of a thin-layer, compact film, prepared by direct sputtering or evaporation on indium tin oxide (ITO)-coated glass substrates. Other preparation methods include sol-gel, chemical vapour deposition and anodic oxidation. The various preparation procedures and the related advantages and drawbacks are described in a series of recent reviews [8-12] to which the reader is referred for details. 

An electrochromic display (ECD) is basically an electrochemical battery where the cyclable energy output is revealed by a colour change. Similarly to any electrochemical cell, the typical configuration of ECDs involves, in sequence, the electrochromic electrode (for instance a WO 3 film deposited on an ITO-coated glass), an electrolyte and a counter-electrode. The electrochromic electrode provides the colour changes while the electrolyte allows the ionic transport and the counter-electrode assures the electrochemical balance. 

Another interesting example of an improved polymer electrolyte for EWs is the poly(ethylene oxide)-polysiloxane hybrid-type electrolyte used by Honda et al [56]. When swollen with propylene carbonate by 160% in weight, this electrolyte reaches at room temperature a conductivity of 10" S cm" and a transmittance of 95% at 550 nm. The use of this electrolyte allowed the realization of laminated EWs using a WO3 electrochromic electrode combined with a Prussian blue counter-electrode. This EW has a response time of about 10 s, i.e. only a factor of 2 slower than that offered by a comparable liquid electrolyte, LiC104-PC-based EW. 

The specific properties of the polymers also open the possibility of exploiting the benefit of plasticity for the realization of revolutionary designs. In fact, it has been shown [66] that the electrochromic electrodes, in... 

The secondary electrode redox reaction is chosen to be a system where there is little perceptible visible color change or as an electrochromic system where the color change is complementary to that of the color change at the primary electrochromic electrode. 

Manda, E. Matsumoto, M. Kawabata, K. Electrochromic electrodes for display devices. Jpn. Kokai Tokkyo Koho JP 01230026, 1989 Chem. Abstr. 1990, 113, 32036. 

ITC) deposited on flexible, plastic substrates such as PMMA or polycarbonate was used as the conductive electrode substrate, with the active electrochromic electrodes producible as a roll which could be attached to window panes with common (e.g. cyanoacrylate) adhesives. This device again optionally used a counter electrode which was also electrochromic, with the difference that it could be not only a metal oxide such as WO3, but also, interestingly, an n-type CP, which of course displays electrochromism which is complementary to that of the more common p-type CPs. Thus, as cathode materials, the p-type CPs P(ANi) s, P(Py) s and poly(phenylene vinylene) were listed as usable, with virtually all the common dopants. As anode materials, WO3, M0O3, poly(isothianaphthene), and the -type CPs poly(alkoxy-thienylene vinylene) poly(p-phenylene), poly(phenyl quinoline) and poly(acetylene) were listed as usable. Liquid nonaqueous electrolytes based on common solvents such as DMSO and THF were used. No electrochromic data were however given in the patent or in subsequent publications. 

Tetrathiafulvalene (TTE) has also been used in electrochromic devices. TTE-based polymers spin-coated onto transparent electrode surfaces form stable thin films with reproducible electrochromic properties (100). The slow response of these devices has been attributed to the rate of ion movement through the polymer matrix. 

Miscellaneous. Iridium dioxide, like RUO2, is useful as an electrode material for dimensionally stable anodes (DSA) (189). SoHd-state pH sensors employing Ir02 electrode material are considered promising for measuring pH of geochemical fluids in nuclear waste repository sites (190). Thin films (qv) ofIr02 ate stable electrochromic materials (191). 

There are various ways in which CMEs can benefit analytical applications. These include acceleration of electron-transfer reactions, preferential accumulation, or selective membrane permeation. Such steps can impart higher selectivity, sensitivity, or stability to electrochemical devices. These analytical applications and improvements have been extensively reviewed (35-37). Many other important applications, including electrochromic display devices, controlled release of drugs, electrosynthesis, and corrosion protection, should also benefit from the rational design of electrode surfaces. 

The enormous efforts put into the basic research and development of conducting polymers are naturally related to hopes of feasible technical apphcations The starting point of this development was the discovery that PA can fimction as an active electrode in a rechargeable polymer battery. Since then, the prospects of technical application have grown considerably Apart from the battery electrode, conducting polymers are discussed as potential electrochromic displays... 

Polynuclear transition metal cyanides such as the well-known Prussian blue and its analogues with osmium and ruthenium have been intensely studied Prussian blue films on electrodes are formed as microcrystalline materials by the electrochemical reduction of FeFe(CN)g in aqueous solutionThey show two reversible redox reactions, and due to the intense color of the single oxidation states, they appear to be candidates for electrochromic displays Ion exchange properties in the reduced state are limited to certain ions having similar ionic radii. Thus, the reversible... 

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