Thin polyfuel membrane

has developed a new, thinner fuel cell membrane that, it claims, delivers the highest power levels ever demonstrated for passive direct methanol fuel cells (DMFCs).

The new hydrocarbon DMFC membrane, with a thickness of 45 microns, delivers 33% more power than the previous industry benchmark, PolyFuel’s 62-micron PolyFuel membrane, which is being use or studied worldwide by original equipment manufacturers (OEMs), particularly in Japan.

The reduced thickness increases performance by reducing the resistivity of the membrane, while allowing a higher level of water back diffusion.

“PolyFuel has been working hard with OEMs to refine its membrane technology to meet their specific needs,” said Jim Balcom, president and CEO of PolyFuel.

“Perhaps the most requested feature has been a thinner membrane that retained the methanol crossover, water crossover and durability advantages of our 62-micron membrane, while meeting aggressive, new fuel cell performance targets. We are pleased that we have been able to specifically engineer a membrane to meet these requests.”

According to Balcom, the new 45-micron membrane’s peak electrochemical performance in passive hardware at 40C is 80 milliwatts per square centimetre of membrane (80mW/cm2) at 0.28V versus 60mW/cm2 for the 62-micron membrane – a 33% improvement that results directly from the 27% reduction in thickness.

Water crossover (EOD) is unchanged from the 62-micron membrane and remains less than 1/2 of competing fluorocarbon membranes. While methanol crossover at open circuit voltage (OCV) now stands at ~57 mA/cm2, slightly above previous levels, but still significantly below that of fluorocarbon membranes. Water back diffusion has been improved by 30% – important for advanced passive fuel cell systems using pure or high concentrations of methanol (fuel).  The test results were obtained on fixtures with fully-passive cathodes, at 40C. Catalyst loading was 8mg/cm2; gas diffusion layers (GDLs) were SGL 10 BA and SGL -10 BC.

Balcom further revealed that in Japan, PolyFuel is now working with six major corporations that are developing DMFC systems, including NEC and Sanyo Electric. Of these six, five are already evaluating the 45-micron membrane for near-term commercial use, including conducting extensive durability and performance testing.

The new membrane will be available in both a hot-bondable version, and a conventional version.