Studies on Proton Transmission across Graphene in Proton-Exchange Membrane Structures

Abstract

This talk will cover a wide range of recent studies involving proton transmission across CVD graphene layers incorporated into proton-exchange-membrane (PEM) sandwich structures. Many low-temperature electrochemical systems including fuel cells and water electrolysis cells involve proton transmission across proton-exchange membranes integrated with electrodes. A key to optimizing such systems is the accomplishment of selective proton transmission at high rates, while simultaneously inhibiting crossover transmission of other molecular species such as water, hydrogen / oxygen, methanol, and other species. Single-layer CVD graphene has been shown to accomplish this. Proton transmission across graphene in Nafion | graphene | Nafion sandwich structures has been shown to occur with an area-normalized resistance of less than 0.05 ohm cm2 at room temperature, with high selectivity relative to other ions. The graphene layer is nearly defect free and should be an excellent barrier to other species besides protons. The talk will include studies of proton transmission rates using hydrogen pump cells, water electrolysis using PEM cells, and related work. Graphene characterization studies using confocal Raman spectroscopy and X-ray photoelectron spectroscopy, and graphene defect characterization using chemical etching of graphene on copper, will also be covered. Effects of the graphene structure (single vs double layer) and the nature of the 2D material (graphene vs. hexagonal boron nitride) on proton transmission rates, and the rates for other ions besides proton, will also be discussed.