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[en] This review focuses on the use of X-ray absorption and emission spectroscopy techniques using hard X-rays to study electrocatalysts under in situ/operando conditions. The importance and the versatility of methods in the study of electrodes in contact with the electrolytes are described, when they are being cycled through the catalytic potentials during the progress of the oxygen-evolution, oxygen reduction and hydrogen evolution reactions. The catalytic oxygen evolution reaction is illustrated with examples using three oxides, Co, Ni and Mn, and two sulfides, Mo and Co. These are used as examples for the hydrogen evolution reaction. A bimetallic, bifunctional oxygen evolving and oxygen reducing Ni/Mn oxide is also presented. The various advantages and constraints in the use of these techniques and the future outlook are discussed.
[en] Clean titanium surfaces were easily obtained by heating samples of the metal under ultra-high vacuum. The thickness of the saturation films of rutile formed on these samples at various air-pressures were then evaluated with a quantitative method using chemical standards. Polycrystalline standards, obtained merely by oxidizing titanium in dry air at 6500C for several minutes, gave practically the same Auger spectra as that obtained on the basal face of monocrystalline rutile. Homogeneity of the thin rutile layer was in all cases corroborated by the behaviour of a hypothetical four-step transition that involves as the precursory step the coupling of the 3d band with an internal-shell, Auger-like process. The proposed quantitative method nay be applied to an homogeneous overlayer of known composition AB on a matrix A, using experimental Auger currents obtained by area determination on the secondary electron distribution curve N(E) = f(E). An expression for the ratio of d/lambdasup(T)sup(i)sub(T)sub(i)sub(O)2, where d is the thickness of the rutile layer and lambda the electron mean free path inside the rutile matrix, was deduced which led to a value for the mean free path in rutile of approx. equal to 18 Angstroem for 387-eV electrons. (orig.)