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In situ monitoring of the phenomenon of electrochemical promotion of catalysis

Espinós, J.P., Rico, V.J., González-Cobos, J., Sánchez-Valencia, J.R., Pérez-Dieste, V., Escudero, C., de Lucas-Consuegra, A., González-Elipe, A.R.
Journal of catalysis 2018 v.358 pp. 27-34
catalytic activity, electrochemistry, electrodes, ions, monitoring, nickel, potassium, spectroscopy, steam
In this work we investigate by in-situ near-ambient pressure photoemission (NAPP) spectroscopy the phenomenon of Electrochemical Promotion of Catalysis (EPOC). We studied the reduction and diffusion kinetics of alkaline ions in a solid electrolyte cell formed by a nickel electrode supported on K⁺-β-alumina electrolyte. Experiments in ultra-high vacuum and in the presence of steam showed that the amount of potassium atoms supplied to the surface is probably affected by nickel electronic modifications induced by adsorbed OH⁻ groups. It was also deduced that part of the segregated potassium would be adsorbed at inner interfaces where it would be inaccessible to the photoelectron analyzer. A migration mechanism of the promoter is proposed consisting in: (i) the electrochemical reduction of the alkali ions (potassium) at the Ni/solid electrolyte/gas interface; (ii) the spillover of potassium atoms onto the Ni gas-exposed surface; and (iii) the diffusion of potassium atoms to Ni inner grain boundary interfaces.