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An inorganic–organic proton exchange membrane for fuel cells with a controlled nanoscale pore structure


Proton exchange membrane fuel cells have the potential for applications in energy conversion and energy storage, but their development has been impeded by problems with the membrane electrode assembly. Here, we demonstrate that a silicon-based inorganic–organic membrane offers a number of advantages over Nafion—the membrane widely used as a proton exchange membrane in hydrogen fuel cells—including higher proton conductivity, a lack of volumetric size change, and membrane electrode assembly construction capabilities. Key to achieving these advantages is fabricating a silicon membrane with pores with diameters of 5–7 nm, adding a self-assembled molecular monolayer on the pore surface, and then capping the pores with a layer of porous silica. The silica layer reduces the diameter of the pores and ensures their hydration, resulting in a proton conductivity that is two to three orders of magnitude higher than that of Nafion at low humidity. A membrane electrode assembly constructed with this proton exchange membrane delivered an order of magnitude higher power density than that achieved previously with a dry hydrogen feed and an air-breathing cathode.

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Figure 1: Schematic of the membrane with functionalized pore wall and thin layers of porous silica on both sides of the membrane.
Figure 2: Fabrication process for the porous silicon membrane.
Figure 3: FTIR spectra of the membrane at different stages of pore surface modification.
Figure 4: Self-assembly of functional groups on the membrane wall of the pores.
Figure 5: Membrane pore size characterization and details of the MEA and its test package.
Figure 6: Performance of the PS–PEM membrane and MEA using a dry hydrogen feed and an air-breathing cathode.


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Financial support for the UIUC team was provided by the Defense Advanced Research Projects Agency (DARPA). C.J.B. was supported through the US Department of Energy, Office of Basic Energy Sciences (grant DE-FG02-02-ER15368) and, Division of Catalysis and Division of Materials Sciences and Engineering. Y.B.J. was supported through the Sandia National Laboratories LDRD program. This work was carried out in part in the Frederick Seitz Materials Research Laboratory Central Facilities, University of Illinois, which are partially supported by the US Department of Energy under grant nos DE-FG02-07ER46453 and DE-FG02-07ER46471. The authors would like to thank T. Spila, R. Haasch and V.V. Mainz for their assistance with the ToF–SIMS, XPS and NMR analysis, and G. Mensing for reviewing the paper. The help of R. Morgan and J. Jihyung in preparing catalysts is also appreciated.

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Authors and Affiliations



S.M. conceived the asymmetric PEM and MEA designs and conceived and performed the self-terminating pore fabrication process as well as modification of the pore surface properties. S.M. performed characterization tests and data analysis. S.M. and M.A.S. discussed the results. E.P. KOH-etched the silicon membranes and deposited the chromium/gold layers. Y.B.J. and C.J.B. performed the PD–ALD work and wrote the corresponding section in the paper. A.R.G. and D.J.B. conducted water desorption tests on some of the membranes. S.M. wrote the paper. M.A.S., C.J.B. and R.I.M commented on the paper.

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Correspondence to Saeed Moghaddam or Mark A. Shannon.

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Moghaddam, S., Pengwang, E., Jiang, YB. et al. An inorganic–organic proton exchange membrane for fuel cells with a controlled nanoscale pore structure. Nature Nanotech 5, 230–236 (2010).

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