260757 Trends in Ammonia Electro-Oxidation On Model Transition Metal Surfaces

Thursday, November 1, 2012: 3:15 PM
318 (Convention Center )
Jeffrey A. Herron, Sara Karraker and Manos Mavrikakis, Department of Chemical and Biological Engineering, University of Wisconsin - Madison, Madison, WI

The electro-oxidation of ammonia (NH3) is a fundamentally important reaction for a number of applications including electrochemical wastewater cleanup, chemical sensing, and hydrogen generation. In addition, there has been interest in utilizing ammonia as an alternative feed for direct fuel cell applications.1  The mechanism for this reaction is not well understood,2 complicating the design of improved electrocatalysts.  Gerischer and Mauerer suggested a mechanism where NH3 is oxidized to some NHx intermediate, which reacts with another NHy intermediate to form an N2Hx+y intermediate.3 This intermediate is subsequently oxidized to N2. Rosca and Koper have demonstrated that the activity on Pt(100) is significantly higher than Pt(111) and they attribute this to the preferential stabilization of NH2 on Pt(100), facilitating dimerization to N2H4.2 Here we present a first principles, periodic density functional theory analysis of  the electrochemical oxidation of NH3on the (111) and (100) facets of Au, Ag, Cu, Pt, Pd, Ni, Ir, Rh to understand: (i) the reaction mechanism and (ii) the experimentally observed structure sensitivity. 

[1] Vidal-Iglesias, F. J.; Solla-Gullon, J.; Montiel, V.; Feliu, J. M.; Aldaz, A., Journal of Power Sources 2007, 171, 448.

[2] Rosca, V.; Koper, M. T. M., Physical Chemistry Chemical Physics 2006, 8, 2513.

[3] Gerischer, H.; Mauerer, A., Journal of Electroanalytical Chemistry 1970, 25, 421.

Extended Abstract: File Not Uploaded
See more of this Session: Rational Catalyst Design II
See more of this Group/Topical: Catalysis and Reaction Engineering Division