Electrochemical and surface characteristics of tin oxide and indium oxide electrodes

Armstrong, Neal R.; Lin, Albert W. C.; Fujihira, Masamichi; Kuwana, Theodore

doi:10.1021/ac60368a035

Cited by 198 publications

(141 citation statements)

References 35 publications

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“…28 It should be noted that the onset of cathodic current on these ITO films has been attributed to partial reduction of surface metal oxides followed by either H + reduction or further reduction of the metal oxides. 29 The microchannel containing the BPEs (Scheme 1b) was filled with air-saturated 0.10 M acetate buffer (pH 4.0). Acetate buffer was used instead of a strong acid such as HClO 4 or H 2 SO 4 because the former is more compatible with ITO and Ag.…”

Section: * S Supporting Informationmentioning

confidence: 99%

Bipolar Electrodes for Rapid Screening of Electrocatalysts

2011

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We report a method for rapid screening of arrays of electrocatalyst candidates. The approach is based on simultaneous activation of the oxygen reduction reaction (ORR) and Ag electrodissolution at the cathodic and anodic poles, respectively, of bipolar electrodes (BPEs). Because the electrochemical activity of the two poles is directly coupled via the BPE, the extent of Ag electrodissolution is directly related to the ORR activity. The screening process lasts ∼12 min. Because Ag dissolution provides a permanent record of catalyst activity, the screening results can be determined by simple optical microscopy after the electrochemical experiment. The method has the potential to provide quantitative information about electrocatalyst activity.H ere we report a new and potentially powerful method for rapid screening of electrocatalysts. The principle is illustrated in Scheme 1, with specific reference to evaluation of the activity of electrocatalysts for the oxygen reduction reaction (ORR). The top frame of Scheme 1a shows an array of three bipolar electrodes (BPEs). 1 The ORR electrocatalyst candidates are deposited onto the cathodic poles of the BPEs, while the anodic poles are composed of parallel Ag microband electrodes. The Ag microbands of each electrode are in electrical contact with one another and with the ORR catalyst via an underlying indium-doped tin oxide (ITO) contact. When a sufficiently high potential (E tot , Scheme 1b) is applied to the solution in the fluidic channel via a pair of driving electrodes, the ORR proceeds at the cathodic poles and the Ag microbands undergo electrodissolution. 2 The efficiency of the ORR catalyst is then determined by counting the number of dissolved Ag microband electrodes: the more bands that dissolve, the better the catalyst. In fact, as we will show, there is a direct thermodynamic link between the overpotential required for the ORR (Scheme 1c) and the number of Ag microbands remaining after the experiment (Scheme 1a). Although we demonstrate this screening method using just three BPEs, arrays of arbitrary size can be monitored in this way with very little additional technological overhead. This is because it is not necessary to make a direct electrical connection to each electrode, which is an intrinsic property of BPEs and the principal reason for using them in an array format. 3 The basic operating principles of BPEs, along with many interesting applications, have been previously described in the scientific literature. 1−14 A driving voltage E tot applied across a microchannel containing a conductive electrolyte solution (Scheme 1b) is dropped nearly linearly over the length of the microchannel. 6 If a conductive wire of sufficient length is present in the microchannel, it will function as a BPE. 1 Specifically, when the interfacial potential differences between the poles of the BPE and the electrolyte solution (ΔE elec , Scheme 1a) are sufficiently high, faradaic processes occur simultaneously: a reduction at the cathodic pole and an oxidation at the a...

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Section: * S Supporting Informationmentioning

confidence: 99%

Bipolar Electrodes for Rapid Screening of Electrocatalysts

2011

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“…However. 50 % of iron tetraphenylporphyrine tetracarboxylic acid which had been condensed onto amino silane on the surface was removed by one week's extraction with DMF [765]. Finklea and Murray reported [757] that the organosilane on the surface was not oxidized by holes produced in the valence band by UV irradiation.…”

Section: ° Nhetmentioning

confidence: 99%

Nature and Estimation of Functional Groups on Solid Surfaces

1983

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“…Over the years, OTEs have been prepared by coating thin films of metals (e.g., gold and platinum), carbon, and metal oxides onto glass or quartz substrates. Of these, indium tin oxide (ITO) films have been the most widely used (11,12). ITO is a Sn(IV)-doped, In 2 O 3 -based n-type semiconductor, which, along with ZnO, has been extensively applied for >20 years to electrooptical devices and photovoltaics (13).…”

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confidence: 99%