Ditty Dixon, Alexander Schröder, Alexander Schökel, Matthias Söhn Darmstadt, Ingo Manke, Nikolay Kardjilov, Tilman Sanders, Volker Loos, Gregor Hoogers, Klaus Wippermann, Detlef Stolten, Christina Roth
May 26, 2013
In situ neutron and X-ray measurements are of essential importance for the rational design of tailor-made catalysts and cell components, in particular when they can be performed with spatial resolution. Neutron radiography allows the investigation of the local fluid distribution in direct methanol fuel cells (DMFCs) under operating conditions with spatial resolutions in the order of some tens of micrometers. In the through-plane mode, an overview of the local water and gas distribution in the flow field channels is obtained, while the in-plane mode provides information on spatially and time resolved fluid distribution across the cell, hydration/dehydration processes and water distribution across the walls of flow field channels. Combined studies of high resolution neutron radiography and segmented cell measurements are especially valuable, because they enable a correlation of the local fluid distribution and local performance. This knowledge is essential in order to optimise water management and performance and to establish a homogeneous fluid, current and temperature distribution in order to achieve high performance and durability of DMFCs. While the neutron studies focus on the cell components, additional information about the catalyst performance and stability is obtained by in situ X-ray absorption spectroscopy (XAS), thus nicely complementing the neutron measurements. Particle size and particle composition as well as degradation processes by oxidation, de-alloying, and particle growth can be probed with spatial resolution during operation. However, both for neutron and X-ray investigations dedicated cell and experiment design are crucial for the success of the measurements.