Graphene Oxide-Intercalated Microbial Montmorillonite to Moderate the Dependence of Nafion-Based PEMFCs in High-Humidity Environments

The most fatal disadvantage of Nafion-based proton-exchange membrane fuel cells (PEMFCs) is their significant performance losses at low relative humidities (RH ≤ 80%), making external humidification necessary. In this work, a graphene oxide (GO)-intercalated microbial montmorillonite (mMMT) layered stack (GO@mMMT) was prepared to enhance the proton conductivity of a Nafion membrane under a low humidity at elevated temperatures. The prepared mMMT had a high specific surface area and pore volume due to microbial mineralization, allowing GO to act as a spacer intercalated between MMT layers. This layered stack greatly enhanced the water absorbance and retention capacity of GO@mMMT/Nafion composite membranes. The GO@mMMT/Nafion composite membrane exhibited excellent proton conductivity under various humidities. Particularly, the 0.5GO@mMMT/Nafion sample achieved a proton conductivity of 36.4 mS·cm –1 at 80 °C/98% RH and 17.3 mS·cm –1 at 80 °C/20% RH, which was 82% and 188% higher than that of the recast Nafion membrane, respectively. The assembled single cell reached a peak power density of 546 mW·cm –2, which was 60% higher than that of the recast Nafion single cell. These results indicate that the Nafion composite membranes with GO@mMMT incorporated layered stacks show substantial potential for PEMFC applications with simplified water management.