Substrate Oxidation Enhances the Electrochemical Production of Hydrogen Peroxide
- Creators
- Lim, Jonghun
- Hoffmann, Michael R.
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.
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).Attached Files
Published - 1-s2.0-S1385894719311891-main.pdf
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Additional details
- PMCID
- PMC6686209
- Eprint ID
- 95812
- Resolver ID
- CaltechAUTHORS:20190528-104654913
- OPP1149755
- Bill and Melinda Gates Foundation
- Created
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2019-05-28Created from EPrint's datestamp field
- Updated
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2021-11-16Created from EPrint's last_modified field