Mechanism of Perchlorate Formation on Boron-Doped Diamond Film Anodes
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- 作者：Orchideh Azizi ; David Hubler ; Glenn Schrader ; James Farrell ; Brian P. Chaplin
- 刊名：Environmental Science & Technology
- 出版年：2011
- 出版时间：December 15, 2011
- 年：2011
- 卷：45
- 期：24
- 页码：10582-10590
- 全文大小：925K
- 年卷期：v.45,no.24(December 15, 2011)
- ISSN：1520-5851
文摘
This research investigated the mechanism of perchlorate (ClO4鈥?/sup>) formation from chlorate (ClO3鈥?/sup>) on boron-doped diamond (BDD) film anodes by use of a rotating disk electrode reactor. Rates of ClO4鈥?/sup> formation were determined as functions of the electrode potential (2.29鈥?.70 V/standard hydrogen electrode, SHE) and temperature (10鈥?0 掳C). At all applied potentials and a ClO3鈥?/sup> concentration of 1 mM, ClO4鈥?/sup> production rates were zeroth-order with respect to ClO4鈥?/sup> concentration. Experimental and density functional theory (DFT) results indicate that ClO3鈥?/sup> oxidation proceeds via a combination of direct electron transfer and hydroxyl radical oxidation with a measured apparent activation energy of 6.9 卤 1.8 kJ路mol鈥? at a potential of 2.60 V/SHE. DFT simulations indicate that the ClO4鈥?/sup> formation mechanism involves direct oxidation of ClO3鈥?/sup> at the BDD surface to form ClO3鈥?/sup>, which becomes activationless at potentials > 0.76 V/SHE. Perchloric acid is then formed via the activationless homogeneous reaction between ClO3鈥?/sup> and OH鈥?/sup> in the diffuse layer next to the BDD surface. DFT simulations also indicate that the reduction of ClO3鈥?/sup> can occur at radical sites on the BDD surface to form ClO3鈥?/sup> and ClO2, which limits the overall rate of ClO4鈥?/sup> formation.