Dresden 2017 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 34: Solid-Liquid Interfaces: Reactions and Electrochemistry - Experiment II
O 34.6: Vortrag
Dienstag, 21. März 2017, 12:00–12:15, HSZ 101
Stability of metallo-porphyrin networks under oxygen reduction and evolution conditions in basic media — •D. Hötger1, C. Morchutt1, M. Etzkorn1, J. Dreiser2, S. Stepanow3, D. Grumelli4, R. Gutzler1, and K. Kern1,5 — 1MPI for Solid State Research, D-70569 Stuttgart — 2SLS, PSI, CH-5232 Villigen — 3ETH Zürich, CH-8092 Zürich — 4CONICET, ARG-1900 La Plata — 5EPFL, CH-1015 Lausanne
Oxygen reduction and evolution reaction (ORR and OER) are two relevant reactions in important devices like fuel cells, electrolysers and metal-air batteries. The catalytic stability of a catalyst is commonly well explored, but little focus is given to the structural integrity of molecule-based catalysts. We study iron-tetrapyridyl porphyrines (FeTPyP) co-deposited with Co on Au(111). The bimetallic network is bifunctionally active for OER and ORR.[1]
FeTPyP-Co is characterized before and after electrocatalysis by scanning tunneling microscopy (STM) to explore the geometric structure of the molecules on the Au(111) surface. STM shows that the molecules remain intact after ORR but decompose during OER. X-ray absorption spectroscopy (XAS) yields insight into the electronic structure of the metal centers. XAS confirms the integrity of TPyP after ORR. In contrast, after OER XAS reveals the presence of Co and Fe oxide on the surface in absence of TPyP. Thus, OER conditions are more aggressive on organic molecules than ORR. This finding is of great importance for the design of molecule-based electrocatalysts.
[1] B. Wurster, et al.; J. Am. Chem. Soc.; 2016, 138, 3623-3626.