Characterization of an amorphous iridium water-oxidation catalyst electrodeposited from organometallic precursors

James D. Blakemore, Michael W. Mara, Maxwell N. Kushner-Lenhoff, Nathan D. Schley, Steven J. Konezny, Ivan Rivalta, Christian F A Negre, Robert C. Snoeberger, Oleksandr Kokhan, Jier Huang, Andrew Stickrath, Lan Anh Tran, Maria L. Parr, Lin X. Chen, David M. Tiede, Victor S. Batista, Robert H. Crabtree, Gary W Brudvig

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Abstract

Upon electrochemical oxidation of the precursor complexes [Cp*Ir(H2O)3]SO4 (1) or [(Cp*Ir)2(OH)3]OH (2) (Cp* = pentamethylcyclopentadienyl), a blue layer of amorphous iridium oxide containing a carbon admixture (BL) is deposited onto the anode. The solid-state, amorphous iridium oxide material that is formed from the molecular precursors is significantly more active for water-oxidation catalysis than crystalline IrO2 and functions as a remarkably robust catalyst, capable of catalyzing water oxidation without deactivation or significant corrosion for at least 70 h. Elemental analysis reveals that BL contains carbon that is derived from the Cp* ligand (∼ 3% by mass after prolonged electrolysis). Because the electrodeposition of precursors 1 or 2 gives a highly active catalyst material, and electrochemical oxidation of other iridium complexes seems not to result in immediate conversion to iridium oxide materials, we investigate here the nature of the deposited material. The steps leading to the formation of BL and its structure have been investigated by a combination of spectroscopic and theoretical methods. IR spectroscopy shows that the carbon content of BL, while containing some C-H bonds intact at short times, is composed primarily of components with C=O fragments at longer times. X-ray absorption and X-ray absorption fine structure show that, on average, the six ligands to iridium in BL are likely oxygen atoms, consistent with formation of iridium oxide under the oxidizing conditions. High-energy X-ray scattering (HEXS) and pair distribution function (PDF) analysis (obtained ex situ on powder samples) show that BL is largely free of the molecular precursors and is composed of small,

Original languageEnglish
Pages (from-to)1860-1871
Number of pages12
JournalInorganic Chemistry
Volume52
Issue number4
DOIs
Publication statusPublished - Feb 18 2013

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Iridium
Organometallics
iridium
catalysts
Oxidation
oxidation
Catalysts
Carbon
Water
Electrochemical oxidation
X ray absorption
water
oxides
electrochemical oxidation
Ligands
carbon
X ray scattering
Electrolysis
Electrodeposition
Powders

ASJC Scopus subject areas

  • Inorganic Chemistry
  • Physical and Theoretical Chemistry

Cite this

Blakemore, J. D., Mara, M. W., Kushner-Lenhoff, M. N., Schley, N. D., Konezny, S. J., Rivalta, I., ... Brudvig, G. W. (2013). Characterization of an amorphous iridium water-oxidation catalyst electrodeposited from organometallic precursors. Inorganic Chemistry, 52(4), 1860-1871. https://doi.org/10.1021/ic301968j

Characterization of an amorphous iridium water-oxidation catalyst electrodeposited from organometallic precursors. / Blakemore, James D.; Mara, Michael W.; Kushner-Lenhoff, Maxwell N.; Schley, Nathan D.; Konezny, Steven J.; Rivalta, Ivan; Negre, Christian F A; Snoeberger, Robert C.; Kokhan, Oleksandr; Huang, Jier; Stickrath, Andrew; Tran, Lan Anh; Parr, Maria L.; Chen, Lin X.; Tiede, David M.; Batista, Victor S.; Crabtree, Robert H.; Brudvig, Gary W.

In: Inorganic Chemistry, Vol. 52, No. 4, 18.02.2013, p. 1860-1871.

Research output: Contribution to journalArticle

Blakemore, JD, Mara, MW, Kushner-Lenhoff, MN, Schley, ND, Konezny, SJ, Rivalta, I, Negre, CFA, Snoeberger, RC, Kokhan, O, Huang, J, Stickrath, A, Tran, LA, Parr, ML, Chen, LX, Tiede, DM, Batista, VS, Crabtree, RH & Brudvig, GW 2013, 'Characterization of an amorphous iridium water-oxidation catalyst electrodeposited from organometallic precursors', Inorganic Chemistry, vol. 52, no. 4, pp. 1860-1871. https://doi.org/10.1021/ic301968j
Blakemore JD, Mara MW, Kushner-Lenhoff MN, Schley ND, Konezny SJ, Rivalta I et al. Characterization of an amorphous iridium water-oxidation catalyst electrodeposited from organometallic precursors. Inorganic Chemistry. 2013 Feb 18;52(4):1860-1871. https://doi.org/10.1021/ic301968j
Blakemore, James D. ; Mara, Michael W. ; Kushner-Lenhoff, Maxwell N. ; Schley, Nathan D. ; Konezny, Steven J. ; Rivalta, Ivan ; Negre, Christian F A ; Snoeberger, Robert C. ; Kokhan, Oleksandr ; Huang, Jier ; Stickrath, Andrew ; Tran, Lan Anh ; Parr, Maria L. ; Chen, Lin X. ; Tiede, David M. ; Batista, Victor S. ; Crabtree, Robert H. ; Brudvig, Gary W. / Characterization of an amorphous iridium water-oxidation catalyst electrodeposited from organometallic precursors. In: Inorganic Chemistry. 2013 ; Vol. 52, No. 4. pp. 1860-1871.
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AU - Blakemore, James D.

AU - Mara, Michael W.

AU - Kushner-Lenhoff, Maxwell N.

AU - Schley, Nathan D.

AU - Konezny, Steven J.

AU - Rivalta, Ivan

AU - Negre, Christian F A

AU - Snoeberger, Robert C.

AU - Kokhan, Oleksandr

AU - Huang, Jier

AU - Stickrath, Andrew

AU - Tran, Lan Anh

AU - Parr, Maria L.

AU - Chen, Lin X.

AU - Tiede, David M.

AU - Batista, Victor S.

AU - Crabtree, Robert H.

AU - Brudvig, Gary W

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N2 - Upon electrochemical oxidation of the precursor complexes [Cp*Ir(H2O)3]SO4 (1) or [(Cp*Ir)2(OH)3]OH (2) (Cp* = pentamethylcyclopentadienyl), a blue layer of amorphous iridium oxide containing a carbon admixture (BL) is deposited onto the anode. The solid-state, amorphous iridium oxide material that is formed from the molecular precursors is significantly more active for water-oxidation catalysis than crystalline IrO2 and functions as a remarkably robust catalyst, capable of catalyzing water oxidation without deactivation or significant corrosion for at least 70 h. Elemental analysis reveals that BL contains carbon that is derived from the Cp* ligand (∼ 3% by mass after prolonged electrolysis). Because the electrodeposition of precursors 1 or 2 gives a highly active catalyst material, and electrochemical oxidation of other iridium complexes seems not to result in immediate conversion to iridium oxide materials, we investigate here the nature of the deposited material. The steps leading to the formation of BL and its structure have been investigated by a combination of spectroscopic and theoretical methods. IR spectroscopy shows that the carbon content of BL, while containing some C-H bonds intact at short times, is composed primarily of components with C=O fragments at longer times. X-ray absorption and X-ray absorption fine structure show that, on average, the six ligands to iridium in BL are likely oxygen atoms, consistent with formation of iridium oxide under the oxidizing conditions. High-energy X-ray scattering (HEXS) and pair distribution function (PDF) analysis (obtained ex situ on powder samples) show that BL is largely free of the molecular precursors and is composed of small,

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