Subproject 4

3D structure-property relationships and operando imaging of the electrolyte distribution

Aim of this subproject is to gain a basic understanding of the relationship between gas/liquid distribution in Ag gas diffusion electrodes (GDE) and their performance. The exact 3D distribution of the liquid and gas phase in the pore system of the Ag-GDEs determines the size of the catalytically active surface at the so-called three-phase boundary (gas-liquid-silver) and is therefore a key element for understanding the functioning of GDEs. In Ag-GDEs, the media distribution significantly depends on the PTFE distribution within the silver pore network. Therefore, the latter is, together with other structural parameters, such as e.g. the pore size distribution, crucial for a possible future improvement of GDEs.

To achieve these goals together with TP3 Roth and TP1 Turek operando measurements are performed to analyze electrolyte distribution by synchrotron/ X-ray imaging. In addition, the pore system and the PTFE distributions of the GDEs are examined with high-resolution (about 5 nm resolution) FIB/SEM tomography and then quantitatively examined by 3D analytical methods (e.g. determination of pore size and tortuosity distributions, PTFE cluster sizes, bottlenecks at pore necks, etc.). The 3D data serve as a template for realistic, real-data-based simulations in the TP5 Nieken, with which the potential 3D transport paths for the electrolyte as well as for the gases are quantified. The results are finally incorporated into the models in TP1 Turek and TP2 Krewer.