Berlin 2018 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

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

O 70.5: Vortrag

Mittwoch, 14. März 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 Cuenya¹ — ¹Department of Physics, Ruhr-University Bochum, Germany — ²Max-Planck-Institut für Eisenforschung, Düsseldorf, Germany — ³Inorganic Chemistry I, Ruhr-University Bochum, Germany

Synthetic pentlandite (Fe_4.5Ni_4.5S₈) 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).