Proton Conductive Material
Applicants: UNIV HOKKAIDO NAT UNIV CORP [JP] / TOYOTA MOTOR CO LTD [JP] / DE 102022119191 A1
This application from Toyota looks to overcome the need for humidification for proton conductive materials. The degree to which this was achieved was tested by immersing in water at 80°C for 1 hour, air drying for 4 days and vacuum drying for a further 24 hours, then weighing the sample. The membrane can be prepared from two different polymers – one being a proton source and the other being a proton channel. Several different chemical groups can release protons, in this case the sulfonic acid group (-SO3H) is preferred and attached to a styrenic group e.g., styrene sulfonic acid (SSA) as shown in Schema 1 below. This type of polymer is chosen because it can form a stacked structure through π-π interactions. The proton channel polymer needs to be able to coordinate protons such as methylene bisacrylamide (MBAA) and is added at 1 part per weight of SSA-Na.
The polymerisation reaction requires an initiator and AMHEPA as shown in Schema 1 below is employed for this purpose. The resulting polymer gel is then treated with 3M aq. HCl and water and vacuum dried for 24 hrs to obtain the final membrane polymer – PolySSA/MBAA. This polymer exhibited 2.9% water loss on testing, however this was presumed due to inadequate drying, and the water resistance would be even higher (although a repeat experiment was not reported).
The work is important for improving the durability of the fuel cell and to prevent disintegration after storage at room temperature, thereby reducing the failure rate and improving the lifetime characteristics.
