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Electrochemical Water Splitting Coupled with Organic Compound Oxidation: The Role of Active Chlorine Species

Park, Hyunwoong and Vecitis, Chad D. and Hoffmann, Michael R. (2009) Electrochemical Water Splitting Coupled with Organic Compound Oxidation: The Role of Active Chlorine Species. Journal of Physical Chemistry C, 113 (18). pp. 7935-7945. ISSN 1932-7447. http://resolver.caltech.edu/CaltechAUTHORS:20150804-121741191

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Abstract

The need for alternative energy sources with minimal to no carbon footprint is growing. A solar-powered electrochemical system that produces hydrogen via water splitting using organic pollutants as sacrificial electron donors is a possible solution. The hybridization of a BiO_x−TiO_2/Ti anode with a stainless steel cathode powered by a photovoltaic (PV) array has been shown to achieve this process. The electrochemical degradation kinetics of a variety of organic substrates is investigated as a function of a background electrolyte, NaCl versus Na_2SO_4. The observed substrate (S) degradation kinetics (k_(obs)^S) are found to correlate well with the cell current (I_(cell)) and the H_2 production energy efficiency (EE) in the presence of NaCl as the background electrolyte. In the case of Na_2SO_4, no correlation is observed and the degradation rates are greatly reduced in comparison to NaCl. This suggests that the primary chemical oxidant is electrolyte-dependent. The k_(obs)^S’s are found to be proportional to the bimolecular rate constants of Cl_2^(•−) with the substrate (k_(Cl_2^(•−) + S)) and to substrate-induced ΔEEs (EE with substrate − EE without substrate) in the presence of NaCl. The ΔEE correlation arises from the active chlorine species acting as an electron shuttle, which compete with H_2 production for cathodic electrons. In the presence of the organic substrates, the active chlorine species are quenched, increasing the fraction of electrons utilized for the H_2 production.


Item Type:Article
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URLURL TypeDescription
http://dx.doi.org/10.1021/jp810331wDOIArticle
http://pubs.acs.org/doi/abs/10.1021/jp810331wPublisherArticle
http://pubs.acs.org/doi/suppl/10.1021/jp810331wPublisherSupporting Information
ORCID:
AuthorORCID
Hoffmann, Michael R.0000-0002-0432-6564
Additional Information:© 2009 American Chemical Society. Received: November 24, 2008; Revised Manuscript Received: February 3, 2009. We are grateful to the Hydrogen Energy Research & Development Center, and 21st Century Frontier Research and Development Program of the Ministry of Science and Technology of Korea for research support. Supporting Information: Kinetic mass balances and steady-state concentrations of the reactive species are provided in Table S1. Reaction rate constants for Cl^• and Cl_2^(•−) reacting with the target substrates are provided in Table S2.
Funders:
Funding AgencyGrant Number
Hydrogen Energy Research and Development CenterUNSPECIFIED
21st Century Frontier Research and Development Program, Ministry of Science and Technology of KoreaUNSPECIFIED
Record Number:CaltechAUTHORS:20150804-121741191
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20150804-121741191
Official Citation:Electrochemical Water Splitting Coupled with Organic Compound Oxidation: The Role of Active Chlorine Species Hyunwoong Park, Chad D. Vecitis, and Michael R. Hoffmann The Journal of Physical Chemistry C 2009 113 (18), 7935-7945 DOI: 10.1021/jp810331w
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:59183
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:05 Aug 2015 22:11
Last Modified:05 Aug 2015 22:11

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