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Decoupled electrochemical water-splitting systems: a review and perspective

Ifkovits, Zachary P. and Evans, Jake M. and Meier, Madeline C. and Papadantonakis, Kimberly M. and Lewis, Nathan S. (2021) Decoupled electrochemical water-splitting systems: a review and perspective. Energy and Environmental Science, 14 (9). pp. 4740-4759. ISSN 1754-5692. doi:10.1039/d1ee01226f.

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Electrochemical water splitting is a promising technology to renewably generate hydrogen fuel from water. One particular drawback of conventional water splitting is that the hydrogen-forming reduction reaction is tightly coupled, both spatially and temporally, to the oxygen-forming oxidation reaction. This coupling poses challenges in both conventional and direct-solar-powered electrolysis systems, including gas crossover and separator degradation, sometimes necessitating the use of precious metal catalysts. In decoupled water splitting, the conventional electrolysis reactions are separated spatially, temporally, or both, via coupling to an intermediate redox mediator. Decoupled water-splitting systems are flexible and modular by nature, with other proposed benefits including facile coupling to renewable power sources, utilization of earth-abundant catalysts, and intrinsically safe operation. Here we review recent advances in decoupled water splitting and related fields, mainly categorizing decoupled systems by mediator phase and standard potential. We offer insight to how decoupling may be advantageous, and which tradeoffs need to be considered for practical implementation. We conclude our review with discussion of known technological hurdles and note opportunities for future discovery.

Item Type:Article
Related URLs:
URLURL TypeDescription
Ifkovits, Zachary P.0000-0003-2538-0794
Evans, Jake M.0000-0002-8721-5316
Meier, Madeline C.0000-0003-1608-0810
Papadantonakis, Kimberly M.0000-0002-9900-5500
Lewis, Nathan S.0000-0001-5245-0538
Additional Information:© The Royal Society of Chemistry 2021. Submitted 24 Apr 2021; Accepted 02 Jul 2021; First published 07 Jul 2021. This material is based upon work performed by the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub, supported through the Office of Science of the U.S. Department of Energy under Award Number DE-SC0004993. MCM acknowledges a Graduate Research Fellowship from the National Science Foundation. MCM also acknowledges the Resnick Sustainability Institute at Caltech for fellowship support. Conflicts of interest: NSL may become a consultant and equity holder in a future potential corporation that is seeking funding to focus on commercial development of catalysts and systems for the production and use of hydrogen.
Group:Resnick Sustainability Institute, JCAP
Funding AgencyGrant Number
Department of Energy (DOE)DE-SC0004993
NSF Graduate Research FellowshipUNSPECIFIED
Resnick Sustainability InstituteUNSPECIFIED
Issue or Number:9
Record Number:CaltechAUTHORS:20210823-225400426
Persistent URL:
Official Citation:Decoupled electrochemical water-splitting systems: a review and perspective. Energy Environ. Sci., 2021, 14, 4740-4759; DOI: 10.1039/d1ee01226f
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:110397
Deposited By: Tony Diaz
Deposited On:24 Aug 2021 17:27
Last Modified:16 Sep 2021 17:08

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