Electrodeposition of highly ordered macroporous iridium oxide through self-assembled colloidal templates

Jin, Hu; Abdelsalam, Mamdouh E.; Bartlett, Philip N.; Cole, Robin M.; Sugawara, Yoshihiro; Baumberg, Jeremy J.; Mahajan, Sumeet; Denuault, Guy

doi:10.1039/b900279k

Cited by 53 publications

(47 citation statements)

References 48 publications

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“…35. Thus, an aliquot of H 2 IrCl 6 solution was added to 50 ml of water (deionised, 18 M ), and stirred for 30 min.…”

Section: Methodsmentioning

confidence: 99%

“…34 the oxalic acid originally used in Ref. 35 was replaced by potassium oxalate, and additional heating was applied to develop the color of the solution more quickly. Also, H 2 IrCl 6 was used instead of anhydrous IrCl 4 , the amount of H 2 IrCl 6 being adjusted to give the same total amount of iridium as in 70 mg of anhydrous IrCl 4 .…”

Section: Methodsmentioning

confidence: 99%

“…Also, H 2 IrCl 6 was used instead of anhydrous IrCl 4 , the amount of H 2 IrCl 6 being adjusted to give the same total amount of iridium as in 70 mg of anhydrous IrCl 4 . 35 This was done based on the mass of iridium (as reported by the supplier) per 1 ml solution.…”

Section: Methodsmentioning

confidence: 99%

“…32 A similar transition was not observed for iridium oxide synthesized by hydrolysis. 17 Electrochemically formed iridium oxide films (EIROFs) 34,35 are particularly interesting forms of iridium oxide from the perspective of making thin iridium oxide layers for high utilization of iridium. Their electronic properties are therefore correspondingly relevant.…”

Section: Iridium Oxidementioning

confidence: 99%

“…Also, various forms of iridium oxide exist, and these may display significant differences in their properties. Thus anodically formed iridium oxide films (AIROFs) display distinct semiconducting behavior in the reduced form and metallic properties in the oxidized form.32 A similar transition was not observed for iridium oxide synthesized by hydrolysis.17 Electrochemically formed iridium oxide films (EIROFs) 34,35 are particularly interesting forms of iridium oxide from the perspective of making thin iridium oxide layers for high utilization of iridium. Their electronic properties are therefore correspondingly relevant.…”

mentioning

confidence: 99%

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Electronic Structure and Growth of Electrochemically Formed Iridium Oxide Films

Ilyukhina

Sunde

Haverkamp

2017

J. Electrochem. Soc.

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The nature of the electronic structure of electrochemically formed iridium oxide films (EIROF) is investigated by in-situ conductivity measurements in an electrochemical cell and ex-situ current-sensing atomic force microscopy (CS-AFM). A direct demonstration of changes in the conductivity for electrochemically formed iridium oxide films (EIROF) with the applied potential of EIROF electrodes in an electrochemical cell is presented. The in-situ conductivity shows a single step-like change at a potential of approximately 1.2 V in 0.5 mol dm −3 H 2 SO 4 vs. a reversible hydrogen reference electrode. The change in conductivity is also reflected in results of ex-situ CS-AFM for EIROF electrodes emersed at different potentials. At an emersion potential of 0 V the CS-AFM currentvoltage characteristics are non-linear and similar to those of diodes. At an emersion potential of 1.6 V the CS-AFM current-voltage characteristics are approximately linear, consistent with metallic behavior. Mott-Schottky analysis shows that at low potentials the oxide behaves as a p-type semiconductor with a flatband potential approximately 500 mV below the transition to high conductivity from the in-situ conductivity measurements. These results allow for an interpretation of changes in the relative magnitudes of the III/IV and IV/V (or IV/VI) voltammetric peaks during film growth through a block-release behavior involving space-charge layers in the oxide. Iridium oxide 1 is relevant as a material for electrochromics, 2-4 electrocatalysis 5-19 and as a pH sensor. 20 A proposed mechanism for the electrochromic properties of the material based on the electronic structure was suggested by Granqvist. 3,4 According to this explanation the change of color with potential is due to variations in band filling associated with intercalation of protons and possibly other ions,where A − is a solution anion, and h • and electron hole. For oxygen-evolution electrocatalysts one expects the activity to depend on the binding energy of intermediates involved in the reaction according to the Sabatier principle. Since the binding energy of the various relevant intermediates appear to scale with the binding energy of oxygen, the latter quantity may serve as a descriptor of catalytic activity for the oxygen evolution reaction. Exactly how the features of the electronic structure of the catalyst are related to the binding energy appears to be less clear than in the case of metals for which the d-band theory and its refinements 22,23 appear to successfully rationalize electronic structure and (electro-) catalytic behavior. Recent work indicates that the number of electrons in the d-band of transition metal oxides is an important descriptor of catalytic activity, 24,25 although other aspects of the electronic structure may be important as well. 26Also other electrochemical properties such as the shapes of voltammograms have been attempted analyzed in terms of electronic structure. 27It is therefore of interest to characterize properties reflecting the electronic struct...

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“…35. Thus, an aliquot of H 2 IrCl 6 solution was added to 50 ml of water (deionised, 18 M ), and stirred for 30 min.…”

Section: Methodsmentioning

confidence: 99%