Comparison of amorphous iridium water-oxidation electrocatalysts prepared from soluble precursors

James D. Blakemore, Nathan D. Schley, Maxwell N. Kushner-Lenhoff, Andrew M. Winter, Francis D'Souza, Robert H. Crabtree, Gary W Brudvig

Research output: Contribution to journalArticle

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Abstract

Electrodeposition of iridium oxide layers from soluble precursors provides a route to active thin-layer electrocatalysts for use on water-oxidizing anodes. Certain organometallic half-sandwich aqua complexes of iridium form stable and highly active oxide films upon electrochemical oxidation in aqueous solution. The catalyst films appear as blue layers on the anode when sufficiently thick, and most closely resemble hydrous iridium(III,IV) oxide by voltammetry. The deposition rate and cyclic voltammetric response of the electrodeposited material depend on whether the precursor complex contains a pentamethylcyclopentadieneyl (Cp*) or cyclopentadienyl ligand (Cp), and do not match, in either case, iridium oxide anodes prepared from non-organometallic precursors. Here, we survey our organometallic precursors, iridium hydroxide, and pre-formed iridium oxide nanoparticles. From electrochemical quartz crystal nanobalance (EQCN) studies, we find differences in the rate of electrodeposition of catalyst layers from the two half-sandwich precursors; however, the resulting layers operate as water-oxidizing anodes with indistinguishable overpotentials and H/D isotope effects. Furthermore, using the mass data collected by EQCN and not otherwise available, we show that the electrodeposited materials are excellent catalysts for the water-oxidation reaction, showing maximum turnover frequencies greater than 0.5 mol O 2 (mol iridium) -1 s -1 and quantitative conversion of current to product dioxygen. Importantly, these anodes maintain their high activity and robustness at very low iridium loadings. Our organometallic precursors contrast with pre-formed iridium oxide nanoparticles, which form an unstable electrodeposited material that is not stably adherent to the anode surface at even moderately oxidizing potentials.

Original languageEnglish
Pages (from-to)7749-7763
Number of pages15
JournalInorganic Chemistry
Volume51
Issue number14
DOIs
Publication statusPublished - Jul 16 2012

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Iridium
electrocatalysts
Electrocatalysts
iridium
Anodes
Oxidation
oxidation
Water
Organometallics
anodes
water
Quartz
oxides
Electrodeposition
Catalysts
Nanoparticles
quartz crystals
catalysts
electrodeposition
Crystals

ASJC Scopus subject areas

  • Inorganic Chemistry
  • Physical and Theoretical Chemistry

Cite this

Blakemore, J. D., Schley, N. D., Kushner-Lenhoff, M. N., Winter, A. M., D'Souza, F., Crabtree, R. H., & Brudvig, G. W. (2012). Comparison of amorphous iridium water-oxidation electrocatalysts prepared from soluble precursors. Inorganic Chemistry, 51(14), 7749-7763. https://doi.org/10.1021/ic300764f

Comparison of amorphous iridium water-oxidation electrocatalysts prepared from soluble precursors. / Blakemore, James D.; Schley, Nathan D.; Kushner-Lenhoff, Maxwell N.; Winter, Andrew M.; D'Souza, Francis; Crabtree, Robert H.; Brudvig, Gary W.

In: Inorganic Chemistry, Vol. 51, No. 14, 16.07.2012, p. 7749-7763.

Research output: Contribution to journalArticle

Blakemore, JD, Schley, ND, Kushner-Lenhoff, MN, Winter, AM, D'Souza, F, Crabtree, RH & Brudvig, GW 2012, 'Comparison of amorphous iridium water-oxidation electrocatalysts prepared from soluble precursors', Inorganic Chemistry, vol. 51, no. 14, pp. 7749-7763. https://doi.org/10.1021/ic300764f
Blakemore JD, Schley ND, Kushner-Lenhoff MN, Winter AM, D'Souza F, Crabtree RH et al. Comparison of amorphous iridium water-oxidation electrocatalysts prepared from soluble precursors. Inorganic Chemistry. 2012 Jul 16;51(14):7749-7763. https://doi.org/10.1021/ic300764f
Blakemore, James D. ; Schley, Nathan D. ; Kushner-Lenhoff, Maxwell N. ; Winter, Andrew M. ; D'Souza, Francis ; Crabtree, Robert H. ; Brudvig, Gary W. / Comparison of amorphous iridium water-oxidation electrocatalysts prepared from soluble precursors. In: Inorganic Chemistry. 2012 ; Vol. 51, No. 14. pp. 7749-7763.
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