Graphene Coating of Nafion Membranes for Enhanced Fuel Cell Performance

Abstract

Electrochemically exfoliated graphene (e-G) thin films on Nafion membranes exhibit a selective barrier effect against undesirable fuel crossover. This approach combines the high proton conductivity of state-of-the-art Nafion and the ability of e-G layers to effectively block the transport of methanol and hydrogen. Nafion membranes are coated with aqueous dispersions of e-G on the anode side, making use of a facile and scalable spray process. Scanning transmission electron microscopy and electron energy-loss spectroscopy confirm the formation of a dense percolated graphene flake network, which acts as a diffusion barrier. The maximum power density in direct methanol fuel cell (DMFC) operation with e-G-coated Nafion N115 is 3.9 times higher than that of the Nafion N115 reference (39 vs 10 mW cm–2@0.3 V) at a 5M methanol feed concentration. This suggests the application of e-G-coated Nafion membranes for portable DMFCs, where the use of highly concentrated methanol is desirable.

Comparative Studies of Atomically Thin Proton Conductive Films to Reduce Crossover in Hydrogen Fuel Cells

“…23−25 Ruhkopf et al showed the application of liquid phase exfoliated graphene decreased methanol crossover in DMFCs by 94.8%, while adversely impacting proton conductivity of the cell by 16.1% with a 200 nm coating. 25 This drastic improvement is attributed to the large difference in kinetic diameters between methanol and protons/water. While the difference in kinetic diameters between water and molecular hydrogen is much less pronounced, the larger diameter of the H 2 molecule suggests that 2D materials might still be effective in hydrogen/air systems in a similar capacity.…”

“…2D materials have thus been integrated into fuel cells, mostly in direct methanol fuel cells (DMFCs) in previous work. − Ruhkopf et al showed the application of liquid phase exfoliated graphene decreased methanol crossover in DMFCs by 94.8%, while adversely impacting proton conductivity of the cell by 16.1% with a 200 nm coating . This drastic improvement is attributed to the large difference in kinetic diameters between methanol and protons/water.…”

Nanocrystalline Boron Nitride Coating for High Conductivity, Low Temperature Proton Exchange Membrane Fuel Cells

“…Several additives to PEM based technologies have been explored in the literature to increase e ciency by reducing crossover, such as recombination layers 11 , 2D material-based crossover mitigation layers 12,13 , and radical scavengers 14 . Amjadi et al illustrated the use of SiO 2 nanoparticles to increase the conductivity of Na on ™ 117 (183 um thick) at low relative humidities (RH), while lowering the crossover 15 .…”

Hollow Nickel Nanochains Coated with Nickel-Iron Hydroxide for Oxygen Evolution

“…These devices are particularly advantageous because they do not emit environmental pollutants, since water and heat are obtained as the reaction byroducts. 4,5 Water electrolysis is a well-known and efficient method for producing high-purity hydrogen. 6−8 The electrolysis process comprises the oxygen evolution reaction (OER) at the anode and the hydrogen evolution reaction (HER) at the cathode.…”

“…Hydrogen can be efficiently used as fuel for electrochemical energy production devices, such as fuel cells. These devices are particularly advantageous because they do not emit environmental pollutants, since water and heat are obtained as the reaction byroducts. , Water electrolysis is a well-known and efficient method for producing high-purity hydrogen. − The electrolysis process comprises the oxygen evolution reaction (OER) at the anode and the hydrogen evolution reaction (HER) at the cathode. The four-electron OER has slower kinetics and a higher overpotential than that of the two-electron HER, which significantly reduces the overall efficiency of water splitting.…”