Structure Investigations of LiMn2O4 as Oxygen Evolution Reaction Catalyst

by Florian Schönewald
Doctoral thesis
Date of Examination:2023-03-06
Date of issue:2023-09-15
Advisor:Prof. Dr. Cynthia A. Volkert
Referee:Prof. Dr. Cynthia A. Volkert
Referee:Dr. Marcel Risch
Persistent Address: http://dx.doi.org/10.53846/goediss-10099

 

 

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Abstract

English

The catalytic activity of a material is determined by the electronic structure and atomic arrangements at its surface. In particular, eg occupancy of octahedral cations has been found to be a successful descriptor of the oxygen evolution reaction (OER) in a variety of materials, including Mn-based spinels. Using scanning transmission electron microscopy (STEM), electron energy loss spectroscopy (EELS) and comparison to electrochemical voltage cycling with a rotating ring-disk electrode (RRDE), it was found that the LixMn2O4 spinel nanoparticles have a core shell structure, which complicates establishing the impact of the near surface eg occupancy on the electrocatalytic oxygen evolution activity. It is indicated that changes of surface eg occupancy do not lead to expected changes of the catalytic activity as reported in literature. Thus, different effects, such as strains introduced in the near surface regions of the nanoparticles by their core-shell geometry, which affect bond distances and Jahn-Teller activity, override the effect of eg occupancy.
Keywords: TEM; OER; Catalysis; Spectroscopy
 
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