Molecular modeling of the morphology and transport properties of two direct methanol fuel cell membranes: phenylated sulfonated poly(ether ether ketone ketone) versus Nafion

Journal Article · Tue Aug 14 04:00:00 EDT 2012 · Journal of Materials Research

DOI:https://doi.org/10.1557/jmr.2012.165· OSTI ID:1047978

Devanathan, Ramaswami; Idupulapati, Nagesh B; Dupuis, Michel

We have used molecular dynamics simulations to examine membrane morphology and the transport of water, methanol and hydronium in phenylated sulfonated poly ether ether ketone ketone (Ph-SPEEKK) and Nafion membranes at 360 K for a range of hydration levels. At comparable hydration levels, the pore diameter is smaller, the sulfonate groups are more closely packed, the hydronium ions are more strongly bound to sulfonate groups, and the diffusion of water and hydronium is slower in Ph-SPEEKK relative to the corresponding properties in Nafion. The aromatic carbon backbone of Ph-SPEEKK is less hydrophobic than the fluorocarbon backbone of Nafion. Water network percolation occurs at a hydration level ({lambda}) of {approx}8 H{sub 2}O/SO{sub 3}{sup -}. At {lambda} = 20, water, methanol and hydronium diffusion coefficients were 1.4 x 10{sup -5}, 0.6 x 10{sup -5} and 0.2 x 10{sup -5} cm{sup 2}/s, respectively. The pore network in Ph-SPEEKK evolves dynamically and develops wide pores for {lambda} > 20, which leads to a jump in methanol crossover and ion transport. This study demonstrates the potential of aromatic membranes as low-cost challengers to Nafion for direct methanol fuel cell applications and the need to develop innovative strategies to combat methanol crossover at high hydration levels.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1047978
• Report Number(s): PNNL-SA-85255; 40083; KC0302020
• Journal Information: Journal of Materials Research, Journal Name: Journal of Materials Research Journal Issue: 15 Vol. 27; ISSN JMREEE; ISSN 0884-2914
• Country of Publication: United States
• Language: English

Related Subjects

10 SYNTHETIC FUELS
30 DIRECT ENERGY CONVERSION
AROMATICS
CARBON
DIFFUSION
DIRECT METHANOL FUEL CELLS
ETHERS
Environmental Molecular Sciences Laboratory
HYDRATION
KETONES
MEMBRANES
METHANOL
MORPHOLOGY
OXONIUM IONS
SIMULATION
SULFONATES
TRANSPORT
WATER
fuel cell
molecular modeling
polymer membrane