Investigating the ionomer structure and interactions in the PEM fuel cell ink by SANS

The proton exchange membrane (PEM) fuel cell is the preferred choice when it comes to power a vehicle by hydrogen. The heart of the fuel cell system is an electrochemical cell, which consists of a membrane sandwiched between two catalyst layers electrodes. During the process of making the catalyst layers, platinum supported on carbon (Pt/C) particles are mixed with ionomer, alcohol, and water. This colloidal suspension is referred to as "ink" The state of the materials within the ink has a huge effect on the final performance and durability of the PEM fuel cell. Previous SANS experiments at ISIS have shown to be very useful to understand the change of the ionomer as a function of the amount of alcohol applied in a dispersion. The SANS helped to create understanding why the addition of alcohol is so important for the ink.

To deeply understand how the ionomer influences the ink structure, it is a necessity to add the Pt/C particles. Ideally, the Pt/C particles would be contrast matched, so that only the ionomer can be observed. For our purposes, the goal would be to use CV-SANS to understand how the ionomer structure evolves around Pt/C particles. The goal would be to quantify the ionomer layer thickness on the Pt/C particles and the amount of free ionomer, which is in the dispersion not deposited on a Pt/C particle.