Successful Effective Sieving of Fuel Molecules Using Graphene Associate Professor Ito et al.
In order to achieve carbon neutrality, there is a growing demand for the development of direct methanol/formic acid fuel cell technology, which uses methanol or formic acid as a synthetic fuel to generate electricity. These fuel cells generate electricity via proton transfer, but conventional proton exchange membranes suffer from the “crossover phenomenon” in which fuel molecules themselves are also transferred between electrodes and unnecessarily oxidized, deactivating the electrode catalysts. In this study, we developed a new proton-exchange membrane with 5 to 10 nm holes in graphene sheets, which are chemically modified with sulfonyl functional groups having sulfo groups around the holes to make them bulky, and succeeded in suppressing the crossover phenomenon by blocking the passage of methanol and formic acid molecules while maintaining high proton conductivity for the first time in the world. This is the first time in the world to succeed in inhibiting crossover phenomena by blocking the passage of methanol and formic acid molecules while maintaining high proton conductivity.
Until now, approaches to inhibit the migration of fuel molecules have included thickening the membrane or sandwiching a two-dimensional material between them. However, these approaches simultaneously reduce proton conductivity. In this study, we investigated structures that inhibit the migration of fuel molecules by electro-osmotic drag and steric hindrance. As a result, it was found that the sulfanyl-modified perforated graphene membrane significantly suppresses electrode deactivation compared to commercially available Nafion membranes, while maintaining the proton conductivity required for fuel cell applications.
It is expected that simply attaching this membrane to a conventional proton exchange membrane will suppress the crossover phenomenon, and this research result will make direct fuel cells a new option other than hydrogen fuel cells.
