Fuel cells and electrolysers have great potential to meet our future energy needs. While there is increasing interest in the development of efficient fuel cell electrocatalysts for alkaline environments, these cells have traditionally suffered from lower activity than acid-based systems. Recently, however, it has been shown that bi-functional Ni-(hydr)oxide/Pt(111) electrocatalysts manifest a ctivities that approach those of acidic fuel cells.In spite of the promising properties of these and related systems, the atomic-scale details underlying their operation remain largely unknown, and the present study focuses on using atomistic computational techniques to elucidate these atomic-scale phenomena.In this talk, we describe a combined thermodynamic and DensityFunctional Theory (DFT) analysis of oxidation/reduction of transition metal (hydr)oxides deposited on precious metal electrocatalyst surfaces. We show how this formalism can be used to develop Pourbaix diagrams and surface phase diagrams of thin (1-2 ML) Ni (hydr)oxide films/islands deposited on close-packed Pt substrates. We then extend these models to describe three-phase boundaries between the films, the Pt substrate, and the surrounding electrolyte, and we study the hydrogen evolution reaction in alkaline media at these interfaces. In the hydrogen evolution region, a partially hydrated-Ni/Pt edge is found to be the most likely candidate for the active phase, and kinetic analysis confirms that H2O dissociation is promoted at these interfaces in comparison to mono-functional Pt catalysts. We close with a discussion of the potential for further improvement of this and related bi-functional electrocatalysts in alkaline environments.References1. �Enhancing Hydrogen Evolution Activity in Water Splitting by Tailoring Li+-Ni(OH)2-Pt Interfaces�R.Subbaraman, D.Tripkovic, D.Strmcnik, KC Chang,M.Uchimura, A. P. Paulikas, V.Stamenkovic, N, M. Markovic,Science 334 (2011) 12562. �Designing 3d-M(Ni,Co,Fe,Mn)-hydr(oxy)oxide catalysts for the water electrolyzerreactions by tuning OH---Mn+ energetics.� R. Subbaraman, D. Tripkovic, K. Chang, D. Strmcnik, A.Paulikas, P. Hirunsit, M. Chan, J. Greeley, V. Stamenkovic, and N. Markovic. Nature Materials 11  (2012) 550.

DFT study of structures and activity of mono- and bifunctional electrocatalysts in alkaline environments

246th National Meeting (2013)

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