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

The prototype chalcogenide electrocatalyst 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 ( , , and ). Theoretically generated XANES on a variety of geometries of adsorption on the predominant phase were compared to the experimental data. We show for the first time that the electrocatalyst first adsorbs in a onefold configuration at lower potentials and -fold at potentials greater than . This expectedly has important consequences for oxygen reduction reaction on alternative chalcogenide materials.