Joseph M. Ziegelbauer

X-Ray Absorption Spectroscopy Studies of Water Activation on an Rh x S y Electrocatalyst for Oxygen Reduction Reaction Applications

The prototype chalcogenide electrocatalyst Rh{sub x}S{sub y} was probed in situ via a synchrotron-based X-ray absorption near-edge structure (XANES) technique to elucidate specific sites and modes of water activation during oxygen reduction reaction. X-ray diffraction revealed a mixture of phases (Rh{sub 2}S{sub 3}, Rh{sub 3}S{sub 4}, and Rh{sub 17}S{sub 15}). Theoretically generated XANES on a variety of geometries of O(H) adsorption on the predominant Rh{sub 3}S{sub 4} phase were compared to the experimental data. We show for the first time that the electrocatalyst first adsorbs O(H) in a one-fold configuration at lower potentials and n-fold at potentials greater than 0.80 V. This expectedly has important consequences for oxygen reduction reaction on alternative chalcogenide materials.