In situ TEM and x-ray spectroscopy studies of perovskite oxide electrodes for electrochemical water oxidation
18.02.2019 von 16:30 bis 17:30
In situ TEM and x-ray spectroscopy studies of perovskite oxide electrodes for electrochemical water oxidation
Christian Jooss
Insitute of Materials Physics, University of Goettingen, Germany
In-situ studies of electro-catalysts are of high interest since they offer the opportunity to study their atomic and electronic structure in the active state in operando. We present environmental Transmission Electron Microscopy (ETEM) and X-ray absorption spectroscopy (XAS) studies of O2 evolution catalysis during H2O splitting in various doped manganite perovskite and Ruddlesden-Popper phases. These systems offer the opportunity for fundamental studies of factors controlling the active site, surface structure and surface defect chemical reactions during water splitting and oxygen evolution.
In Manganite perovskites, such as Pr1-xCaxMnO3 and La1-xSrxMnO3, the involvement of metal centers or lattice oxygen as an active site in OER depends on the electronic band structure. Depending on the hybridization of oxygen and manganese states, either lattice oxygen or manganese sites or cation vacancies can be involved in water splitting. This leads to entirely different surface defect reaction as mechanisms influencing the stability of the surface. Active states of electrodes can show a highly dynamic motion of surface atoms, relevant for mechanistic understanding of the O-O bond formation process. The different behavior of the selected manganites with respect to defect chemistry under OER conditions is explained based on ab initio calculations, where the doping trends are correlated to induced changes of the electronic band structure.
The talk will include an introduction into method aspects of in situ ETEM and XAS studies, in order to give support the significance of the in situ observations for real world electro-chemistry.
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