Spectroscopy and imaging

About

In order to develop efficient electrochemical energy converters, a fundamental understanding of the underlying electrochemical processes is necessary. Using model systems, we investigate the relevant chemical reactions of electrolysis and fuel cells at the interface between the electrode and electrolyte under conditions that correspond to the planned operation. We apply vibrational spectroscopic techniques such as infrared and Raman spectroscopy in combination with atomistic simulations and imaging analysis techniques such as electron and atomic force microscopy.

Research Topics

Our basic investigations focus, for example, on materials for polymer electrolyte membrane fuel cells. The use of ionic liquids as a proton-conducting electrolyte promises to raise the operating temperature, which means a significant increase in efficiency. To further optimize these novel electrolytes, we analyze the interaction between the electrolyte, electrode, and polymer membrane.

Contact

Dr. Christian Rodenbücher

IEK-14

Building 03.11 / Room 2002

+49 2461/61-6142

E-Mail

Polymer electrolyte membrane fuel cells (PEMFC)

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Interfaces between proton-conducting ionic liquids and catalytic electrodes

The behavior of ionic liquids differs fundamentally from that of conventional aqueous electrolytes since they consist solely of charged molecular ions. This is particularly true for the electrochemical double layer at the interface to a polarized electrode. A compact structure of alternating anion and cation layers is formed, which also influences reactions crucial for fuel cell operation (e.g. oxygen reduction). We investigate this interfacial structure and its dependence on residual water content using atomic force microscopy as well as infrared and Raman spectroscopy.

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Investigation of PBI membranes for HT-PEMFCs

For use in the high-temperature range between 120 °C and 200 °C, special membranes are required, the conductivity of which does not depend on the presence of water. We explore how proton conduction can be induced in polybenzimidazole (PBI) by doping with phosphoric acid and ionic liquids. To develop models for the conductivity mechanism in the membrane as well as between the membrane and catalytic electrode, we produce prototype membranes and analyze their electrochemical properties as well as their chemical composition and morphology.

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Solid oxide materials

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Double perovskites as novel SOC electrode materials

Double perovskites are promising candidates for use as catalytic electrode materials for alkaline electrolysis and solid oxide cells (SOCs) that operate at temperatures below 600 °C. Their ordered structure enables both efficient electronic transport and good conductivity for oxygen ions. We study the details of the relationships between the crystallographic structure and electrochemical properties by synthesizing and analyzing ceramics and thin films with a particular focus on surfaces and interfaces.

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Solid-state reactions under electric and chemical potential gradients

To improve the lifetime of solid oxide converters, we study the effect of (electro)chemical potential gradients that occur, for example, during electrolysis operation on the properties of electrode and electrolyte materials. Emphasis is placed on the local ionic and electronic transport at extended defects such as dislocations and grain boundaries, since they are potential weak points of the material and thus of the overall system. We conduct electroreduction experiments, which help us to selectively induce material transformations leading to the formation of new phases, and thus to establish models for oxide degradation.

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(Fast) ion conduction along solid-solid phase boundaries

Ion conduction in solid electrolyte insulator multilayers is studied in systems with single layer thicknesses of down to 10 nm. It shows that the interfacial strains have an effect on the local ion transport, which enables microstructured solid electrolytes with optimized properties.

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Last Modified: 23.01.2023