Electrochromic electrode

Figure 9 Absorption spectrum (a) and electrochromism (b) of [Ru(bpy)3] dissolved in a thin polymer film at 77 K. Absorption and electrochromism spectra are taken through semitransparent conducting electrodes. Electrochromism is usually measured with the externally applied electric field parallel to the propagation direction koflight( = 0°). Experiments can also be made with the film tilted away from the normal to the propagation direction (Drawn from data in Oh and Boxer )...

Flexible electrochromic devices (ECDs) are becoming increasing important for their promising applications in many areas, such as the portable and wearable electronic devices, including smart windows, functional supercapacitors, and flexible displays. Typically, an ECD consists of four parts of substrate, conductive electrode, electrochromic material, and electrolyte. Enormous efforts have been made to improve the flexibility of ECDs including utilizing flexible polymer substrates and conductive materials. 

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... 

Figure 33.1a illustrates the idea of the smart window. In this device a layer of electrochromic material and a layer of a transparent ion-conducting electrolyte are sandwiched between two optically transparent electrodes (OTEs). Indium-doped tin oxide on glass is used most commonly as the OTE. This material has very low... 

If an anodically colored electrochromic material (e.g., Ir02) is used as one electrode in the device in Eig. 33.1fi and a cathodically colored (e.g., WO3) is used as the other electrode, a much larger change in transmission per charge supplied can be seen compared to the case when only one electrode is electrochromic. Also, the use of an intercalation material as the counter electrode may be advantageous for the device shown in Eig. 33.1a, as it can minimize undesired reactions on the counter electrode. 

Polymers films formed from tr i sbipvr idineruthenium complexes and coated on electrode surfaces have been found to have interesting electrochromic and conductivity properties. 

Iridium as an electrode material has received considerable attention in the last decade not only because of its excellent catalytic properties but also in relation to the electrochromic effect observed for anodic iridium oxide films (AIROF). Electrochromism of iridium was thought to be of technical relevance for display applications and triggered several studies of the electrochemical and optical properties of AlROFs [67, 85-88],... 

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... 

Electrochromic materials (either as an electroactive surface film or an electroactive solute) are generally first studied at a single working electrode, under potentiostatic or galvanostatic control, using three-electrode circuitry.1 Traditional electrochemical techniques such as cyclic voltametry (CV), coulometry, and chronoamperometry, all partnered by in situ spectroscopic measurements... 

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... 

Kashiwazaki67 has fabricated a complementary ECD using plasma-polymerized ytterbium bis(phthalocyanine) (pp—Yb(Pc)2) and PB films on ITO with an aqueous solution of 4M KC1 as electrolyte. Blue-to-green electrochromicity was achieved in a two-electrode cell by complementing the green-to-blue color transition (on reduction) of the pp—Yb(Pc)2 film with the blue (PB)-to-colorless (PW) transition (oxidation) of the PB. A three-color display (blue, green, and red) was fabricated in a three-electrode cell in which a third electrode (ITO) was electrically connected to the PB electrode. A reduction reaction at the third electrode, as an additional counter electrode, provides adequate oxidation of the pp Yb(Pc)2 electrode, resulting in the red coloration of the pp—Yb(Pc)2 film. 

Garcia-Canadas, J.Meacham, A. P.Peter, L. M.Ward, M. D. Electrochromic switching in the visible and near IR with a Ru-dioxolene complex adsorbed on to a nanocrystalline Sn02 electrode. Electrochem. Commun. 2003, 5, 416 120. 

Kobayashi T., Yoneyama H., Tamura H. Polyaniline film-coated electrodes as electrochromic display devices J.Electroanal.Chem., 1984 161 429-23... 

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