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Multiphase Nanostructure of a Quinary Metal Oxide Electrocatalyst Reveals a New Direction for OER Electrocatalyst Design

Haber, Joel A. and Anzenburg, Eitan and Yano, Junko and Kisielowski, Christian and Gregoire, John M. (2015) Multiphase Nanostructure of a Quinary Metal Oxide Electrocatalyst Reveals a New Direction for OER Electrocatalyst Design. Advanced Energy Materials, 5 (10). Art. No. 1402307. ISSN 1614-6832. doi:10.1002/aenm.201402307.

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Ce-rich mixed metal oxides comprise a recently discovered class of -electrocatalysts for the oxygen evolution reaction (OER). In particular, at current densities below 10 mA cm^(−2), Ni_(0.3)Fe_(0.07)Co_(0.2)Ce_(0.43)O_x exhibits ¬superior activity compared to the corresponding transition metal oxides, despite the relative inactivity of ceria. To elucidate the enhanced activity and underlying catalytic mechanism, detailed structural characterization of this quinary oxide electrocatalyst is reported. Transmission electron microscopy imaging of cross-section films as-prepared and after electrochemical testing reveals a stable two-phase nanostructure composed of 3–5 nm diameter crystallites of fluorite CeO_2 intimately mixed with 3–5 nm crystallites of transition metal oxides alloyed in the rock salt NiO structure. Dosing experiments demonstrate that an electron flux greater than ≈1000 e Å^(−2) s^(−1) causes the inherently crystalline material to become amorphous. A very low dose rate of 130 e Å^(−2) s^(−1) is employed for atomic resolution imaging using inline holography techniques to reveal a nanostructure in which the transition metal oxide nanocrystals form atomically sharp boundaries with the ceria nanocrystals, and these results are corroborated with extensive synchrotron X-ray absorption spectroscopy measurements. Ceria is a well-studied cocatalyst for other heterogeneous and electrochemical reactions, and our discovery introduces biphasic cocatalysis as a design concept for improved OER electrocatalysts.

Item Type:Article
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URLURL TypeDescription Information
Haber, Joel A.0000-0001-7847-5506
Yano, Junko0000-0001-6308-9071
Kisielowski, Christian0000-0001-6425-0779
Gregoire, John M.0000-0002-2863-5265
Additional Information:© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. Received: December 23, 2014; Revised: January 23, 2015; Published online: February 27, 2015. This work was performed by the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub, supported through the Office of Science of the U.S. Department of Energy under Award No. DE-SC000499. Electron microscopy was performed at the Molecular Foundry which is supported by the Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. Electron transparent samples were prepared by M. Libbee at the Molecular Foundry. XAS data collection was carried out at the Stanford Synchrotron Radiation Lightsource (SSRL) beamline 7-3, operated by Stanford University for the U.S. DOE Office of Science, and supported by the DOE Office of Biological and Environmental Research, and by the NIH (including P41GM103393), and the Advanced Light Source (ALS) beamline 10.3.2, supported by DOE under Contract No. DE-AC02-05CH11231. The authors thank Dr. Ravishankar Sundararaman for insight into the equilibrium phase behavior of this system and Dr. Suho Jung for assistance with electrochemical experiments.
Funding AgencyGrant Number
Department of Energy (DOE)DE-SC0004993
Department of Energy (DOE)DE-AC02-05CH11231
Issue or Number:10
Record Number:CaltechAUTHORS:20150615-085042878
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Official Citation:Haber J. A., Anzenburg E., Yano J., Kisielowski C., Gregoire J. M. (2015). Multiphase Nanostructure of a Quinary Metal Oxide Electrocatalyst Reveals a New Direction for OER Electrocatalyst Design. Adv. Energy Mater., 5: . doi: 10.1002/aenm.201402307
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:58234
Deposited By: Tony Diaz
Deposited On:15 Jun 2015 18:09
Last Modified:10 Nov 2021 22:01

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