Improved Ionomers and Membranes for Fuel Cells
- Tetramer Technologies, LLC
- National Renewable Energy Laboratory (NREL), Golden, CO (United States)
- Plug Power, Inc., Latham, NY (United States)
Background: Fuel cells, capable of generating electricity from renewable green fuels such as hydrogen, are regarded as vital to development of a carbon-neutral energy economy. Proton exchange membrane (PEM) based hydrogen fuel cells are particularly favored due to their potential for efficient, quiet, clean operation, producing water as the sole emission. The dominant membrane technology for PEM fuel cells is currently based on variants of perfluorosulfonic acid (PFSA) originally introduced by Dupont as Nafion™. However, in spite of their extensive use, PFSA ionomers and membranes suffer significant disadvantages, including poor performance and chemical stability at (highly desirable) elevated temperatures (>90 oC) and under low humidity conditions and high cost. In addition, PFSA materials, their precursors and degradation products have recently become the focus of growing environmental and toxicological concerns and regulations. Purpose of the Research: The primary objective of this Phase II project was to further develop a series of novel non-PFSA ionomers and membranes for commercial application in PEM fuel cells. Approach: A significant advantage of this non-PFSA ionomer technology is the flexibility to accommodate a large number of possible structural variations in functionality and morphology. During Phase II, these advantages were exploited through systematic modification and optimization of Phase I down-selected structures. In addition to optimizing performance, factors such as excessive water uptake, which can lead to membrane instability and poor durability, were addressed. For example, custom crosslinking procedures, developed previously at Tetramer, were applied alongside modification of molecular weight, blending with elastomeric resins and incorporation of mechanical supports. Ionomer and membrane development were carried out at Tetramer and membranes supplied to our collaborators for specialty evaluation and testing using both standard Department of Energy developed protocols and proprietary commercial conditions. Results: To date, this work has led to the development of two series of PEMs which have demonstrated improved performance properties (including good proton conductivity and low hydrogen crossover) compared with leading commercial PFSA membranes, under both standard operating conditions and at elevated temperatures (e.g., 95 °C). Short term performance and durability have been successfully demonstrated using accelerated stress test (AST) protocols at both the National Renewable Energy Laboratory (NREL) and the fuel cell production facilities of our commercial partner Plug Power. These novel PEMs also successfully met device performance requirements in Plug Power's commercial stacks. In addition, approaches were successfully demonstrated to allow further customization of key physical and chemical properties affecting both efficiency and long term durability. Control over water uptake, mechanical stability, ion exchange capacity, proton conductivity and hydrogen permeability was demonstrated. Applications: Direct applications of this work include next generation heavy duty, long distance commercial transportation, material handling (e.g., emission free, rapid refuel forklifts), stationary and backup power generators, and portable specialty devices. The development of more efficient, versatile fuel cell technologies will play a significant role on reducing dependence on fossil fuels and the associated economic, political and environmental issues related to their extraction, refinement, supply and final use.
- Research Organization:
- Tetramer Technologies, LLC
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- SC0019980
- OSTI ID:
- 1984800
- Type / Phase:
- SBIR (Phase II)
- Report Number(s):
- DOE-Tetramer-19980
- Country of Publication:
- United States
- Language:
- English
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