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Effects of Electrolyte Buffer Capacity on Surface Reactant Species and Reaction Rate of CO_2 in Electrochemical CO_2 Reduction

Hashiba, Hiroshi and Weng, Lien-Chun and Chen, Yikai and Sato, Hiroki K. and Yotsuhashi, Satoshi and Xiang, Chengxiang and Weber, Adam Z. (2018) Effects of Electrolyte Buffer Capacity on Surface Reactant Species and Reaction Rate of CO_2 in Electrochemical CO_2 Reduction. Journal of Physical Chemistry C, 122 (7). pp. 3719-3726. ISSN 1932-7447. doi:10.1021/acs.jpcc.7b11316.

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In the aqueous electrochemical reduction of CO_2, the choice of electrolyte is responsible for the catalytic activity and selectivity, although there remains a need for more in-depth understanding of electrolyte effects and mechanisms. In this study, using both experimental and simulation approaches, we report how the buffer capacity of the electrolytes affects the kinetics and equilibrium of surface reactant species and resulting reaction rate of CO_2 with varying partial CO_2 pressure. Electrolytes investigated include KCl (non-buffered), KHCO3 (buffered by bicarbonate), and phosphate buffered electrolytes. Assuming 100% methane production, the simulation successfully explains the experimental trends of maximum CO_2 flux in KCl and KHCO_3, and also highlights the difference between KHCO_3 and phosphate in terms of pKa as well as the impact of buffer capacity. To examine the electrolyte impact on selectivity, the model is run with a constant total current density. Using this model, several factors are elucidated including the importance of local pH, which is not in acid/base equilibrium, the impact of buffer identity and kinetics, and the mass-transport boundary-layer thickness. The gained understanding can help optimize CO_2 reduction in aqueous environments.

Item Type:Article
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URLURL TypeDescription Information
Xiang, Chengxiang0000-0002-1698-6754
Weber, Adam Z.0000-0002-7749-1624
Alternate Title:Effects of Electrolyte Buffer Capacity on Surface Reactant Species and Reaction Rate of CO2 in Electrochemical CO2 Reduction
Additional Information:© 2018 American Chemical Society. Received: November 15, 2017; Revised: January 19, 2018; Published: January 30, 2018. The material is based on work performed at the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub, as follows: The constant flux simulations were supported through the Office of Science of the U.S. Department of Energy under award no. DE-SC0004993. The experimental work and the limiting-current simulations and analysis were supported by Panasonic Corporation under a JCAP Industrial Partnership Agreement. The authors declare no competing financial interest.
Funding AgencyGrant Number
Department of Energy (DOE)DE-SC0004993
Issue or Number:7
Record Number:CaltechAUTHORS:20180131-150900860
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Official Citation:Effects of Electrolyte Buffer Capacity on Surface Reactant Species and the Reaction Rate of CO2 in Electrochemical CO2 Reduction. Hiroshi Hashiba, Lien-Chun Weng, Yikai Chen, Hiroki K. Sato, Satoshi Yotsuhashi, Chengxiang Xiang, and Adam Z. Weber. The Journal of Physical Chemistry C 2018 122 (7), 3719-3726 DOI: 10.1021/acs.jpcc.7b11316
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:84611
Deposited By: Tony Diaz
Deposited On:01 Feb 2018 00:37
Last Modified:15 Nov 2021 20:21

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