379657 In Situ Studies of the Active Sites in Nife Oxyhydroxides for the Electrochemical Oxidation of Water

Tuesday, November 18, 2014: 9:30 AM
306 (Hilton Atlanta)
Alexis T. Bell, Department of Chemical and Biomolecular Engineering, University of California at Berkeley, Berkeley, CA

A key challenge to the development of photoelectrochemical devices that can generate hydrogen from water using solar energy is the discovery design criteria for new, efficient and stable electrocatalysts for the oxygen evolution reaction (OER). Here, we identify the origin of a 500-fold OER activity enhancement that can be achieved with mixed (Ni,Fe)oxyhydroxides (Ni1-xFexOOH) over their pure Ni and Fe parent compounds, resulting in one of the most active known OER catalysts in alkaline electrolyte. Operando XAS measurements reveal that Fe3+ in Ni1-xFexOOH occupies octahedral sites with unusually short Fe-O bond distances, induced by edge-sharing with surrounding [NiO6] octahedra. Using DFT calculations, we establish that this structural motif results in near optimal adsorption energies of OER intermediates and low overpotentials at Fe sites. By contrast, Ni sites in Ni1-xFexOOH are not active sites for the oxidation of water.

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