Graphene coating of Nafion$^{(R)}$ membranes for enhanced fuel cell performance

TL;DR

This study demonstrates that coating Nafion membranes with electrochemically exfoliated graphene significantly enhances fuel cell performance by reducing fuel crossover and increasing power density, especially at high methanol concentrations.

Contribution

The paper introduces a scalable spray coating method of graphene on Nafion membranes, creating an effective diffusion barrier that improves direct methanol fuel cell efficiency.

Findings

Maximum power density increased 3.9 times with graphene coating.

Graphene layers effectively block methanol and hydrogen crossover.

Coated membranes perform better at high methanol concentrations.

Abstract

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