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Vapor-fed electrolysis of water using earth-abundant catalysts in Nafion or in bipolar Nafion/poly(benzimidazolium) membranes

Giesbrecht, Patrick K. and Müller, Astrid M. and Read, Carlos G. and Holdcroft, Steven and Lewis, Nathan S. and Freund, Michael S. (2019) Vapor-fed electrolysis of water using earth-abundant catalysts in Nafion or in bipolar Nafion/poly(benzimidazolium) membranes. Sustainable Energy and Fuels, 3 (12). pp. 3611-3626. ISSN 2398-4902. https://resolver.caltech.edu/CaltechAUTHORS:20191029-113947239

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Abstract

Vapor-fed electrolysis of water has been performed using membrane-electrode assemblies (MEAs) incorporating earth-abundant catalysts and bipolar membranes (BPMs). Catalyst films containing CoP nanoparticles, carbon black, and Nafion were synthesized, characterized, and integrated into cathodes of MEAs. The CoP-containing MEAs exhibited stable (>16 h) vapor-fed electrolysis of water at room temperature at a current density of 10 mA cm⁻² with 350 mV of additional overvoltage relative to MEA's formed from Pt/C cathodic electrocatalysts due to slower hydrogen-evolution reaction kinetics under vapor-fed conditions and fewer available triple-phase boundaries in the catalyst film. Additionally, catalyst films containing a [NiFe]-layered double hydroxide ([NiFe]-LDH) as well as a hydroxide ion conductor, hexamethyl-p-terphenyl poly(benzimidazolium) (HMT-PMBI), were synthesized, characterized, and integrated into the anodes of the MEAs. The [NiFe]-LDH-containing MEAs exhibited overvoltages at 10 mA cm⁻² that were similar to those of IrO_x-containing MEAs for vapor-fed electrolysis of water at room temperature. A BPM was formed by pairing Nafion with HMT-PMBI, resulting in a locally alkaline environment of HMT-PMBI to stabilize the [NiFe]-LDH and a locally acidic environment to stabilize the CoP. BPM-based MEAs were stable (>16 h) for vapor-fed electrolysis of water at room temperature at a current density of 10 mA cm⁻², with a change in the pH gradient of 1 unit over 16 h of electrolysis for IrOx-containing MEAs. The stability of [NiFe]-LDH-based MEAs under vapor-fed conditions was dependent on the catalyst film morphology and resulting BPM interface, with stable operation at 10 mA cm⁻² achieved for 16 h. All MEAs exhibited a drift in the operating voltage over time associated with dehydration. These results demonstrate that earth-abundant catalysts and BPMs can be incorporated into stable, room-temperature, vapor-fed water-splitting cells operated at 10 mA cm⁻².


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1039/c9se00672aDOIArticle
http://www.rsc.org/suppdata/c9/se/c9se00672a/c9se00672a1.pdfPublisherSupporting Information
ORCID:
AuthorORCID
Giesbrecht, Patrick K.0000-0003-2039-4791
Müller, Astrid M.0000-0002-2785-6808
Lewis, Nathan S.0000-0001-5245-0538
Freund, Michael S.0000-0003-1104-2292
Additional Information:© 2019 The Royal Society of Chemistry. The article was received on 17 Aug 2019, accepted on 23 Oct 2019 and first published on 28 Oct 2019. Support for this work was provided by the United States National Science Foundation (NSF) under the CCI Solar Fuels Program, Grant No. CHE-1305124, the Natural Sciences and Engineering Research Council of Canada (NSERC), as well as the Canada Foundation for Innovation (CFI). We are grateful to Kimberly Papadantonakis for helpful comments and technical editing of the manuscript. There are no conflicts to declare.
Group:CCI Solar Fuels
Funders:
Funding AgencyGrant Number
NSFCHE-1305124
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
Canada Foundation for InnovationUNSPECIFIED
Issue or Number:12
Record Number:CaltechAUTHORS:20191029-113947239
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20191029-113947239
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:99536
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:29 Oct 2019 20:30
Last Modified:21 Nov 2019 17:40

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