University of Electro-Communications research: Combination imaging reveals fuel cell damage

Fuel cells have the potential to provide clean energy for powering vehicles, but improved performance and durability are needed for wide-spread commercialisation. A collaboration of researchers in Japan has now demonstrated a technique for simultaneously mapping the morphology as well as electronic and bonding states on fuel cell electrode membranes for the first time. The results show how the catalysts on the membrane electrodes degrade and provide insights for improving the durability.

Yasuhiro Iwasawa and colleagues from the University of Electro-Communications, the University of Tokushima and the Japan Synchrotron Radiation Research Institute studied proton exchange membrane fuel cells based on Nafion – an ion-containing polymer (ionomer) widely used for these devices. In their report of the results they point out how they might expect the non-uniform distribution of catalytic platinum nanoparticles to lead to non-uniform degradation throughout the fuel cell. As a result spatially resolved imaging of the membrane and catalytic platinum chemical species is key to determining how to reduce the deterioration of the catalyst, and hence improve the durability.

The researchers combined scanning transmission electron microscopy (STEM) and energy dispersive X-ray spectroscopy (EDS) techniques with X-ray absorption fine structure measurements (XAFS). “The STEM/EDS can give morphological information on atomic arrangement and element distribution, while the nano-XAFS can give molecular-level chemical information on electronic (oxidation) states and coordination structures with chemical bonding,” they explain in their report of the work.

By using their same-view STEM/EDS and XAFS equipment to compare the membranes before and after 300 cycles of gas exchange, they were able to identify two processes causing irreversible degradation of the platinum catalyst: detachment of the platinum nanoparticles from the carbon support and the formation of platinum ions. Further they found that these processes were dependent on the ratios of platinum and ionomer.