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Berlin 2018 – scientific programme

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O: Fachverband Oberflächenphysik

O 70: Solid-liquid interfaces: Reactions and electrochemisty III (joint session O/CPP)

O 70.5: Talk

Wednesday, March 14, 2018, 16:00–16:15, MA 144

Operando Phonon Studies of the Protonation Mechanism in Highly Active Hydrogen Evolution Reaction Pentlandite Catalysts — •Ioannis Zegkinoglou1, Ali Zendegani2, Ilya Sinev1, Ulf-Peter Apfel3, Tilmann Hickel2, and Beatriz Roldan Cuenya11Department of Physics, Ruhr-University Bochum, Germany — 2Max-Planck-Institut für Eisenforschung, Düsseldorf, Germany — 3Inorganic Chemistry I, Ruhr-University Bochum, Germany

Synthetic pentlandite (Fe4.5Ni4.5S8) is a promising electrocatalyst for hydrogen evolution, demonstrating high current densities, low overpotential, and remarkable stability in bulk form. The depletion of sulfur from the surface of this catalyst during the electrochemical reaction has been proposed to be beneficial for its catalytic performance. We have performed electrochemical operando studies of the vibrational dynamics of pentlandite under hydrogen evolution reaction conditions using 57Fe nuclear resonant inelastic X-ray scattering [1]. Comparing the measured Fe partial vibrational density of states with DFT calculations, we have demonstrated that hydrogen atoms preferentially occupy substitutional positions replacing pre-existing sulfur vacancies. Once all vacancies are filled, the protonation proceeds interstitially, which slows down the reaction. Our results highlight the beneficial role of sulfur vacancies in the electrocatalytic performance of pentlandite and give insights into the hydrogen adsorption mechanism during the reaction. [1] I. Zegkinoglou et al., J. Am. Chem. Soc. 139, 14360 (2017).

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