Evaluation of Neutron Imaging for Measuring Phosphoric Acid Distribution in High Temperature PEFCs

The possibility of using neutron imaging for non-invasive investigation of the phosphoric acid distribution in high temperature polymer electrolyte fuel cells (HT-PEFC) was explored with a small scale test cell. In particular, the issue of providing a suitable reference – necessary for distinguishing the neutron attenuation due to the acid from the attenuation due to the structural components – was solved by using in situ deuteration/protonation of the phosphoric acid, a fully reversible process. Experiments with a non-operating cell have shown that this isotope exchange can be performed in less than 20 minutes. The possibility of imaging the acid distribution either over the cell area ( through-plane imaging) or across the cell structure ( in-plane imaging) was demonstrated. Although some discrepancies between the two modes remain, quantitative analysis resulted in a good agreement with the amount of acid used in the cell.