The hydrogen evolution on platinum is a milestone reaction in electrocatalysis as well as an important reaction towards sustainable energy storage. Remarkably, the pH dependent kinetics of this reaction is not yet fully understood. Here, we present a detailed kinetic study of the hydrogen adsorption and evolution reaction on Pt(111) in a wide pH range. Impedance and Tafel slope measurements show that the hydrogen adsorption and hydrogen evolution are both slow in alkaline media, which is consistent with the observation of a shift in the rate-determining step for H2 evolution.Adding nickel to the Pt(111) surface lowers the barrier for the hydrogen adsorption rate in alkaline solutions and thereby enhances the hydrogen evolution rate. These observations are explained by a new model which highlights the role of the reorganization of interfacial water to accommodate charge transfer through the electric double layer, the energetics of which is controlled by how strongly water interacts with the interfacial field. The new model is supported by laser-induced temperature-jump measurements. Our model sheds new light on the origin of the slow kinetics for the hydrogen evolution reaction in alkaline media.

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Cobalt hydroxide species are at the origin of OER activity of multiheteroatom doped carbon catalysts.

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2014 Des mesures ultrasonores aux basses températures, dans la gamme de fréquence 0,1-1 GHz ont été faites sur le verre magnétique (MnF2)0,65(BaF2)0,2(NaPO3)0,15. La densité spectrale, P des systèmes à 2 niveaux (S2N) est deux ordres de grandeur plus petite que dans les autres verres tandis que les constantes de couplage S2N-phonon 03B31 et 03B3t sont anormalement grandes. La comparaison avec les mesures effectuées sur le verre non magnétique (ZnF2)0,6(BaF2)0,2(NaPO3)0,2 suggère un lien entre ces valeurs anormales et les propriétés magnétiques du verre.