Young Investigator Group Zeis

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Fuel Cells

Fuel cells are among the enabling technologies toward a safe, reliable, and sustainable energy solution. Yet the lack of clean hydrogen sources and a sizable hydrogen infrastructure limits the fuel-cell applications today. Due to their elevated operating temperature, between 150°C and 180°C, high-temperature proton exchange membrane fuel cells (HT-PEMFCs) based on phosphoric acid doped polybenzimidazole (H3PO4/PBI) membranes can tolerate fuel contaminants such as carbon monoxide (CO) and hydrogen sulfide (H2S) without considerable performance loss. These are typical byproducts of the steam reforming process, which produces hydrogen from hydrocarbon fuels such as methanol or natural gas. So it is an appealing concept to couple a HT-PEMFC stack directly with a fuel processor, which can be used as auxiliary power units (APUs).  These APUs use the fossil fuel resources more efficiently and help reduce emission of CO2. This might also be a good strategy for the wide deployment of fuel cells before the hydrogen infrastructure is established. The fuel cell system’s efficiency can be further increased by reusing the exhaust heat produced during electrical power generation.

One of the group’s core competences is the development of high-temperature membrane electrode assemblies (MEAs). By optimizing its key components, the membrane and the electrode, we were able to fabricate high-performing and durable single cells. We specifically investigate the doping process of AB-PBI membranes, the stability and performance of novel acid base blend membrane, the morphology and wettability of the gas diffusion electrodes, and platinum alloy catalyst.

Vanadium Redox Flow Batteries

Vanadium Redox Flow Batteries (VRFBs) provide an attractive solution for large-scale (Megawatt and higher) energy storage. It is desirable to further improve the energy cycle efficiency by reducing energy losses during charging and discharging. Porous carbon materials are commonly used as electrodes in this type of batteries. These materials need to have continuous pathways to allow for reactant movement. We monitor this movement by visualizing the electrolyte flow through the porous carbon electrodes using synchrotron X-ray tomography. This reveals the flow dynamics within the porous materials, helps us understand the impact of saturation on the mass transport of the electrolyte, and quantifies the loss of active reaction sites due to low electrolyte penetration.

We are also investigating changes in carbon fiber structures of these materials at different stages of the life cycle, starting from as received, to activation, and then ageing. The changes in morphology of the carbon material and its functional groups show the impact of activation and ageing on the surface properties and consequently the performance of the cell itself. Differential Electrochemical Mass Spectrometry helps us track typical side reactions in VRFBs that hamper these batteries’ performance.