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Substrate Oxidation Enhances the Electrochemical Production of Hydrogen Peroxide

Lim, Jonghun and Hoffmann, Michael R. (2019) Substrate Oxidation Enhances the Electrochemical Production of Hydrogen Peroxide. Chemical Engineering Journal, 374 . pp. 958-964. ISSN 1385-8947 . http://resolver.caltech.edu/CaltechAUTHORS:20190528-104654913

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Abstract

Hydrogen peroxide (H_2O_2) is electrochemically produced via oxygen (O_2) reduction on a carbon cathode surface. In order to enhance the production of H_2O_2, anodic loss pathways, which significantly reduce the overall H_2O_2 production rate, should be inhibited. In this study, we investigate the effects of organic electron donors (i.e., typical chemical contaminants) on the anodic loss pathways of H_2O_2 in a single-cell electrochemical reactor that employs an anode composed of TiO_2 over-coated on a mixed-metal oxide ohmic contact catalyst, Ir_(0.7)Ta_(0.3)O_2, deposited on a Ti-metal that is coupled with a graphite rod cathode in a sodium sulfate (Na_2SO_4) electrolyte that is saturated with oxygen (O_2). Organic electron donors are shown to enhance the electrochemical production of H_2O_2, while simultaneously undergoing oxidative degradation. The observed positive effect of organic electron donors on the electrochemical production of H_2O_2 is due in part to a preferential adsorption of organic substrates on the TiO_2 outer layer of the anode. The sorption of the organic electron donors inhibits the formation of surficial titanium hydroperoxo species ( Ti-OOH) on the anode surface. The organic sorbates also act as scavengers of surface-bound hydroxyl radical Ti-OH. As a result, the decomposition of H_2O_2 on the anode surface is significantly reduced. The cathodic production rate of H_2O_2 at low pH is enhanced due to proton coupled electron transfer (PCET) to O_2, while the anodic decomposition of H_2O_2 is inhibited due to electrostatic interactions between negatively-charged organic substrates and a positively-charged outer surface of the anode (TiO_2 pH_(zpc) = 5.8) at low pH.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1016/j.cej.2019.05.165DOIArticle
ORCID:
AuthorORCID
Hoffmann, Michael R.0000-0002-0432-6564
Additional Information:© 2019 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/BY/4.0/). Received 6 February 2019, Revised 22 May 2019, Accepted 24 May 2019, Available online 25 May 2019. This research was supported by the Bill and Melinda Gates Foundation (OPP1149755).
Funders:
Funding AgencyGrant Number
Bill and Melinda Gates FoundationOPP1149755
Subject Keywords:electrocatalysis; hydrogen peroxide; anodic decomposition of H2O2; organic electron donors
Record Number:CaltechAUTHORS:20190528-104654913
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20190528-104654913
Official Citation:Jonghun Lim, Michael R. Hoffmann, Substrate oxidation enhances the electrochemical production of hydrogen peroxide, Chemical Engineering Journal, Volume 374, 2019, Pages 958-964, ISSN 1385-8947, https://doi.org/10.1016/j.cej.2019.05.165. (http://www.sciencedirect.com/science/article/pii/S1385894719311891)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:95812
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:28 May 2019 20:17
Last Modified:11 Jun 2019 18:55

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