Graphene-Based Proton Transmission and Hydrogen Crossover Mitigation in Electrochemical Hydrogen Pump Cells

The relative rates of transmembrane proton and hydrogen gas transmission are of high importance in most PEM-based electrochemical energy conversion devices. Membrane separators that simultaneously have high rates of proton transmission and low rates of gas transmission are highly desired but this property combination is difficult to achieve because most modifications that could give higher proton transmission rates through a membrane, tend also to give higher gas crossover rates. This presentation will present results indicating that one monolayer of CVD single-layer graphene embedded between two polyelectrolyte membranes can give this desired membrane property combination. Proton transmission occurs through single-layer graphene in a PEM sandwich structure with area-specific resistance values less than 40 mΩ cm2, which is less than the resistance of most PEM membranes. Hydrogen crossover rates in PEM / graphene / PEM sandwich structures were measured by a limiting current method and found to be reduced by more than eight times relative to values in similar membranes without graphene. The lecture will present data on these points and discuss the mechanism(s) by which graphene might provide this desirable set of membrane properties.