Spurgeon, Joshua M. and Walter, Michael G. and Zhou, Junfeng and Kohl, Paul A. and Lewis, Nathan S. (2011) Electrical conductivity, ionic conductivity, optical absorption, and gas separation properties of ionically conductive polymer membranes embedded with Si microwire arrays. Energy and Environmental Science, 4 (5). pp. 1772-1780. ISSN 1754-5692 http://resolver.caltech.edu/CaltechAUTHORS:20110519-094752518
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The optical absorption, ionic conductivity, electronic conductivity, and gas separation properties have been evaluated for flexible composite films of ionically conductive polymers that contain partially embedded arrays of ordered, crystalline, p-type Si microwires. The cation exchange ionomer Nafion, and a recently developed anion exchange ionomer, poly(arylene ether sulfone) that contains quaternary ammonium groups (QAPSF), produced composite microwire array/ionomer membrane films that were suitable for operation in acidic or alkaline media, respectively. The ionic conductivity of the Si wire array/Nafion composite films in 2.0 M H_(2)SO_4(aq) was 71 mS cm^(−1), and the conductivity of the Si wire array/QAPSF composite films in 2.0 M KOH(aq) was 6.4 mS cm^(−1). Both values were comparable to the conductivities observed for films of these ionomers that did not contain embedded Si wire arrays. Two Si wire array/Nafion membranes were electrically connected in series, using a conducting polymer, to produce a trilayer, multifunctional membrane that exhibited an ionic conductivity in 2.0 M H_(2)SO)4(aq) of 57 mS cm^(−1) and an ohmic electrical contact, with an areal resistance of ~0.30 Ω cm^2, between the two physically separate embedded Si wire arrays. All of the wire array/ionomer composite membranes showed low rates of hydrogen crossover. Optical measurements indicated very low absorption (<3%) in the ion-exchange polymers but high light absorption (up to 80%) by the wire arrays even at normal incidence, attesting to the suitability of such multifunctional membranes for application in solar fuels production.
|Additional Information:||© 2011 Royal Society of Chemistry. Received 11th January 2011, Accepted 23rd February 2011. First published on the web 28 Mar 2011. This work was supported by the Department of Energy, Office of Basic Energy Sciences, DE-FG02-07ER46405 and by DARPA contract #W911NF-09-2-0011. We acknowledge use of facilities supported by the Caltech Center for Science and Engineering of Materials, an NSF MRSEC, and the Caltech Center for Sustainable Energy Research. The financial support (J.Z. and P.K.) from the Army Research Laboratory, contract LCHS22067 is gratefully acknowledged. M.G.W. acknowledges the financial support from an NSF-ACCF postdoctoral fellowship (CHE-0937048).|
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|Deposited By:||Jason Perez|
|Deposited On:||20 May 2011 20:08|
|Last Modified:||20 May 2011 20:08|
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