Anodic coloration

Table 2. Some Anodically Colored, Inorganic Insertion/Extraction Films...

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. 

The number of protons extracted from the film during coloration depends on the width of the potential step under consideration. As can be seen in the formulation of Fig. 26 an additional valence state change occurs at 1.25 Vsce giving rise to another proton extraction. The second proton exchange may explain the observation by Michell et al. [91] who determined a transfer of two electrons (protons) during coloration. Equation (5) is well supported by XPS measurements of the Ir4/ and Ols levels of thick anodic iridium oxide films emersed at different electrode potentials in the bleached and coloured state. Deconyolution of the Ols level of an AIROF into the contribution of oxide (O2-, 529.6 eV) hydroxide, (OH, 531.2 eV) and probably water (533.1 eV) indicates that oxide species are formed during anodization (coloration) on the expense of hydroxide species. The bleached film appears to be pure hydroxide (Fig. 27). 

Anodically colored electrochromic inorganic films, 6 579-580 Anodic cleaning, 9 783, 785 Anodic (passivating) corrosion inhibitors, 26 144... 

Electrochromic displays, 6 572t, 582—583 Electrochromic foil device, laminated polyester- based, 23 22 Electrochromic materials, 6 571-587 anodically colored inorganic films, 6 579-580... 

Dnring the process of colouration in electrochromic cells by passing a charge in one direction, a colour can form in one or both of the electrodes or in the electrolyte adjacent to the electrodes. When the colour is formed by reduction at a negative electrode it is called cathodic coloration and, conversely, at the anode it is anodic coloration. Two different types of cells are shown schematically in Figure 1.31. ... 

An electrochromic device embodies a number of superimposed layers on a transparent substrate or between two transparent substrates, and optical transmittance is altered when an electrical potential is applied so that charge is shuttled between layers serving in the same way as anodes and cathodes in an electrical battery. One specific design with a five-layer construction shown in Figure 30 uses cathodically coloring WO3 and anodically coloring nickel oxide joined by an ion-conducting electrolytic laminate. A potential of a few volts, preferably supplied by solar cells, is applied between... 

An electrochromic cell is schematically formed by three main layers electrochromic material/ion conductor (electrolyte)/ion storage layer (counter electrode). Since the different oxides can colour either in anodic (NiO) or in cathodic (WO3) polarization, it is interesting to make the counter electrode also an active material, and to associate electrochromic materials with cathodic coloration as well as anodic coloration. In practice, there are seven successive layers, as shown in Figure 14.1(a). 

The cel with PB was cycled for more than 3500 scans (52 days). In coloration, the dark blue colour was lost for pale blue. To recover it properties, the cell must be left at the anodic coloration potential during times from 10 minutes to 1 hour. 

Reeves, B.D., B.C. Thompson, K.A. Abboud, B.E. Smart, and J.R. Reynolds. 2002. Dual cathodically and anodically coloring electrochromic polymer based on a spiro bipropylenedioxythiophene [poly(spiroBiProDOT)]. Adv Mater 14 717-719. 

This industry includes various types of plating, anodizing, coloring, forming, and ftnishing operations. The metal-finishing industry operations are related closely to those of many other industries, including transportation (automobile parts and accessories), electrical, and jewelry. 

The homopolymer (PSATE) and copolymer P (SATE-co-Th) of succinic acid bis(2-thiophen-3-ylethyl) ester with thiophene obtained by Sacan et al. showed a contrast of 16 and 34 % and response times of 2.3 and 1.5 s, respectively, indicating that the copolymer had a shorter response time, higher contrast and higher stability. These polymers may serve as anodically coloring materials for use in ECD applications [62]. 

Most of the conjugated polymers such as polythiophene and its 3-substituted derivatives are anodically coloring, and are deeply colored in their oxidized forms with a dark blue to black color and a red to purple color in their reduced and neutral forms, respectively. Although this type of color change can be useful, a more desirable color change would be one in which the polymer switches from a highly colored state to a highly transmissive state. 

A new bipropylenedioxythiophene, poly(spiroBiProDOT), has been reported with dual cathodically and anodically coloring properties, displaying three different colors in the oxidized, neutral and reduced states [61, 73]. (l-Phenylethyl)-2,5-di(2-thienyl)-17f-pyrrole [P(PETPy)] was used as the anodically coloring material and PEDOT as the cathodically coloring electrochromic material for dual-type ECDs [4]. 

Dual-type polymer electrochromic devices based on copolymers of 2-benzyl-5,12-dihydro-27f-pyrrolo [3, 4 2,3] [1, 4]dioxocino[6,7-6]quinoxaline (DPOQ) and 5,12-dihydrothieno[3, 4 2,3] [1, 4]dithiocino [6,7- >]quinoxaline (DTTQ) with bithiophene were developed. P (DPOQ-co-BT) and P(DTTQ-co-BT) were used as the anodically coloring and PEDOT as the cathodically coloring electrochromic materials [81]. Each device performed with a favorable switching time, optical contrast, open-circuit memory and stability. 

Table 4.60. Titanium anodization color vs. applied voltage...

The bandgap of PEDOT ( g = 1.6-1.7 eV)itselfis 0.5 eV lower than polythiophene, which results in an absorbance maximiun in the NIR region. Compared to other substituted polythiophenes, these materials exhibit excellent stability in the doped state which is associated with high conductivity. Doped PEDOT is almost transparent in the visible region (with a sky-blue tint) and the neutral polymer is deep blue. Because PEDOT and its alkyl derivatives are cathodically-coloring electrochromic materials, they are suitable for use with anodically-coloring conducting polymers in the construction of dual polymer ECDs (63). 

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