Structured functional materials for multiple transport in nanoscale spatial constraints

Fuel cells utilize the controlled chemical conversion of oxygen and hydrogen into water, releasing electrical energy in the process. Thus, this technology, in combination with green hydrogen, offers a promising alternative for transitioning to a more climate-neutral energy infrastructure. An important prerequisite for a highly efficient system is the catalyst used, which is usually the expensive noble metal platinum. Its optimal utilization is enabled by tailor-made nanostructured and often modified catalyst particles with a large active surface area. However, the efficiency of the system is not only influenced by the catalyst used. An aspect not to be neglected is the transport process of all involved reactants during the reaction, as well as ion, electron, and heat flows. The resulting complexity is a significant challenge for system optimization, and deciphering it is a crucial step towards the commercial implementation of fuel cell systems.

In the Collaborative Research Center 1585 "MultiTrans" at the University of Bayreuth, the aforementioned multiple transport processes are at the center of scientific interest. Project A02: "Proton & H₂O Transport in Functionalized Porous Electrode Structures," jointly led by Prof. Dr.-Ing. Christina Roth (Chair of Materials Processing Engineering) and Prof. Dr. Rhett Kempe (Chair of Inorganic Chemistry II), focuses on high-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) and the associated challenges. Compared to the better-known and better-researched low-temperature fuel cell, this cell type brings many advantages, such as a reduced susceptibility to impurities and catalyst poisons like CO introduced through the gas stream. Despite these advantages, several fundamental problems hinder the commercial application of this cell type. Among other things, phosphoric acid is used as a temperature-stable electrolyte in HT-PEMFCs, but it is flushed out during operation with the product water or even poisons active catalyst centers. One goal of this project is therefore the effective immobilization of the electrolyte within the fuel cell, achieved by confining phosphoric acid in electrically conductive and hollow carbon nanofibers (CNF), which form a porous electrode structure. The described CNFs are produced using an electrospinning process from selected polymer precursors with controllable porosity and conductivity.

In addition, the resulting effects of this spatial confinement of the electrolyte on the remaining parallel process sequences inside the fuel cell will be thoroughly investigated.

Project Profile

Duration: 01.10.2023 - 30.09.2026

Funding: Deutsche Forschungsgemeinschaft (DFG)

Contact: Sven Hörnig, Prof. Dr.-Ing. Christina Roth