Advances in Hydrocarbon Membrane Development at PolyFuel

 

Advances in Hydrocarbon Membrane Development at PolyFuel

 

PolyFuel successfully introduced DM-1 its first generation DMFC membrane in 2003.  Since then several versions of that product have been introduced including thickness ranging from 20 to 62 microns as well as processability improvements.  Key characteristics of PolyFuel's 1st generation DMFC membrane are low methanol crossover, good power density and low water flux.  Based on these characteristics and the resultant benefits of smaller, lighter, and less costly systems, PolyFuel now has a 44% market share of the demonstration prototype systems shown around the world. 

The DM-1 range of products are perfectly suited for certain system architectures and they still available; however, new membrane products are under development at PolyFuel to address new, more advanced, system designs.  With these advancing system designs, the membrane requirements have evolved, and not all in the same direction!

Customer requirements for next generation membranes fall into 3 principal groups; (i) higher power density, (ii) lower methanol crossover and (iii) higher water diffusivity.  These requirements each pull the membrane properties in diverging directions and PolyFuel has 3 membrane engineering programs underway to meet these needs. 

While there are distinct and divergent groupings of requirements, there are also areas of overlap.  For example, in combination with higher power density, several customers also desire higher water flux for both active and passive system without sacrificing rapid beak-in, recovery from dry out and mechanical properties.  Some increase in methanol crossover is acceptable in certain system given MEA designs that can reduce methanol concentrations at the membrane surface.

PolyFuel will present the latest results from all three of these membrane development programs in the Fuel Cell Seminar paper, including the following performance and water flux data from a promising experimental membrane - EXP-109 - being developed in the high power density membrane program.  See figures 1 and 2 for performance and water flux data respectively.

Figure 1.  EXP-109 Polarization Curve

Figure 2. EXP-109 & DM-1 Electro-osmotic Drag as a Function of Temperature

In addition to impressive performance and water flux, the EXP-109 membrane exhibits remarkable resilience to very demanding dry-out conditions.  For example, a membrane was forced to dry-out insitu by flowing air at 500 sccm over both sides of the cell for 16 hours.  Membrane resistance rise was monitored during the dry-out and measured at over 10 times the typical operating resistance at the end of the 16 hour dry-out.  Following the dry-out the cell was restarted using the normal operating conditions, 1 M methanol at 2.3 cm3/min for 1 minute prior to starting the air flow and load.  Stable resistance in the original operating range was obtained within minutes and full performance and transport properties return to the baseline state within 1 hour of operation in these standard conditions.