Novel Membrane Fabrication and Development for Low Temperature Electrolysis and PEC
LaboratoryNational Renewable Energy Laboratory (NREL)
Capability ExpertBryan Pivovar, Kelly Meek, Christopher Antunes
Process and Manufacturing Scale-Up
Node Readiness Category1: Low-Temperature Electrolysis (LTE)
For >5 years, NREL has been a leader in membrane synthesis, fabrication, and characterization in the field of anion exchange membranes for fuel cell applications. The tools and experience acquired from these ongoing projects can be directly leveraged into the production of membranes from various chemistries, either proton or anion-exchange, for use in low temperature electrolysis and PEC research. NREL scientists have engineered AEM polymer chemistries from a wide variety of polymer synthesis/modification techniques. Our experience includes working with both hydrocarbon and fluorocarbon backbones, optimizing side chain chemistries, and developing new, base-stable cationic groups. Our work with AEMs can easily be extended to proton exchange membranes (PEMs) if deemed necessary for electrolysis/PEC application. We commonly use hand-spread, doctor blade, and Meyer rod techniques to fabricate membranes up to 300 cm2 from these polymer solutions. For non-soluble polymers, we have successfully melt-pressed polymer powders into homogeneous membranes. Temperature-controlled presses and vacuum ovens enable whatever membrane pre-treatment may be necessary. Characterization techniques include but are not limited to conductivity, water uptake, automated ion exchange capacity titration, TGA/DSC, NMR, SAXS, DMA, and microscopy. Where NREL is most unique is its ability to produce membranes at pilot industrial scale and with novel reinforcement morphologies. The custom-built roll-to-roll coating station is equipped with multiple coating technologies (including slot-die and micro-gravure), two separate heating ovens, with the ability to coat onto any substrate at industrially relevant speeds. This equipment allows NREL to scale-up successful membrane chemistries into large batch rolls, which would facilitate single-cell and stack testing for electrolysis membrane electrode assemblies (MEAs). In addition, a dual-fiber electrospinner has been designed and built in-house, which allows for intimate polymer mixing on the nano-scale and enables the blending/mechanical reinforcement of ion exchange membranes. Membranes with heterogeneous gradient composition and bipolar/amphoteric morphologies can also be fabricated.
NREL tools and techniques facilitate membrane production from in-house synthesized polymers ranging from small scale single batches to large scale pilot rolls. These capabilities can be extended to support membrane production from both proton exchange and anion exchange polymers developed by other scientists for use in electrolysis MEAs.
The roll-to-roll and dual-fiber electrospinning capabilities, and concomitant staff experience, represent a unique contribution to the national laboratory skill set. Working with numerous iterations of anion exchange polymers for alkaline fuel cells has afforded the NREL staff with valuable experience in the various quirks of membrane fabrication and how to overcome them.
All tools are located in the Energy Systems Integration Facility at NREL, whose goal is to facilitate outside collaborations with the NREL staff. There are no limitations to this use.
The membrane fabrication tools at NREL enable the characterization and testing of novel membranes for electrolysis MEAs and potentially allow the scale-up of successful membranes for distribution.
(clockwise from top left): Zoom-in of roll coater, roll-to-roll station, dual fiber electrospinning apparatus, hot press, Meyer rods and doctor-blade, example membrane.
A.M. Park et al., Crosslinked poly (phenylene oxide)-based nanofiber composite membranes for alkaline fuel cells. Journal of Materials Chemistry A 4 (1), 132-141. "Advanced Ionomers & MEAs for Alkaline Membrane Fuel Cells," B. Pivovar; Annual Merit Review, Hydrogen and Fuel Cells Program. June 2016.