Graphene Filter Could Protect Fuel Cells From Big Molecules

A University of Tsukuba research team has successfully developed a new method that can prevent the crossover of large fuel molecules and suppress the degradation of electrodes in advanced fuel cell technology using methanol or formic acid.

The successful sieving of the fuel molecules is achieved via selective proton transfers due to steric hindrance on holey graphene sheets that have chemical functionalization and act as proton-exchange membranes.

The research reporting paper “Suppression of Methanol and Formate Crossover through Sulfanilic‐Functionalized Holey Graphene as Proton Exchange Membranes,” has been published in the journal Advanced Science.

For realizing carbon neutrality, the demand for the development of direct methanol/formic acid fuel cell technology has been increasing. In this technology, methanol or formic acid is used as an e-fuel for generating electricity. The fuel cells generate electricity via proton transfer; however, conventional proton-exchange membranes suffer from the “crossover phenomenon,” where the fuel molecules are also transferred between anodes and cathodes. Thereafter, the fuel molecules are unnecessarily oxidized and the electrodes are deactivated.

The successful sieving of the fuel molecules is achieved via selective proton transfers due to steric hindrance on holey graphene sheets that have chemical functionalization and act as proton-exchange membranes. Image Credit: Yoshikasu Ito, University of Tsukuba. For more information and images click the open access study paper link here.

In this study, the researchers developed a new proton-exchange membrane comprising graphene sheets with 5-10 nm-diameter holes, which are chemically modified with sulfanilic functional groups affording sulfo groups around the holes. Owing to steric hindrance by the functional groups, the graphene membrane successfully suppresses the crossover phenomenon by blocking the penetration of the fuel molecules while maintaining high proton conductivity for the first time to the best of the team’s knowledge.

To date, conventional approaches for inhibiting fuel-molecule migration involved an increase of the membrane thickness or sandwiching two-dimensional materials, which in turn reduced the proton conductivity. In this study, the researchers investigated structures that inhibit the migration of fuel molecules through electro-osmotic drag and steric hindrance. That’s how they found that the sulfanilic-functionalized graphene membrane can remarkably suppress electrode degradation compared with the commercially-available Nafion membranes while maintaining the proton conductivity required for fuel cells.

Furthermore, simply pasting the graphene membrane onto a conventional proton-exchange membrane can suppress the crossover phenomenon. Thus, this study contributes to the development of advanced fuel cells as a new alternative for hydrogen-type fuel cells.

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While fuel cells are not fully mass market ready their potential simply from an efficiency standpoint is just outstanding. The fuel cell technology could mature to the point a few gallons of liquid fuel could propel a vehicle very far very efficiently.

Fuel energizing a fuel cell making electricity sent to a motor would be elegantly simple and offer quite a lot of power and tremendous range.

Fuel cell power might be the only successful way to electrify a large part of the transportation fleet.

The progress continues, but there is still a quite way to go.

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