Gas diffusion electrodes for environmental applications
Gas diffusion electrodes for environmental applications
A new type of uncatalysed gas diffusion electrode based on screen printing a C/PTFE mixture onto carbon fibre paper has been tested and studied for the reduction of oxygen to hydrogen peroxide. It is confirmed that hydrogen peroxide can be produced at a high rate in alkaline solution by the cathodic reduction of oxygen at an uncatalysed XC72-R carbon gas diffusion electrode For electrolyses carried out at constant current, in the range of 10-200 mA cm-2, the hydrogen peroxide concentration is seen to increase linearly with charge (to a limiting concentration of ~50mM). Moreover, the current efficiencies achievable are in excess of 90%. Voltammetry studies at each electrode in alkaline solution show iR drop to be distorting the responses.
The electrodes were applied successfully to the destruction of low levels of organics in synthetic aqueous effluents and media with pH between 1 and 3 were examined. In these acidic sulphate media, the effect of iR drop is shown to be more severe. The limitation, again, appears to be associated with an iR drop in the electrolyte within the pores of the carbon powder/PTFE active layer and this difficulty is magnified by the relatively low conductivity of the solutions used in this work. Oxygen is, however, reduced in these acid solutions and current densities of ~100 mA cm-2 can be reached. As the pH was decreased the current efficiency for hydrogen peroxide production appeared to drop but this results from chemical decomposition of hydrogen peroxide in homogeneous solution. Although hydrogen peroxide does not appear to be stable in the low acidity, the successful removal of several organics (phenol, aniline, acetic acid, formaldehyde and three azo-dyes) from aqueous solution at pH 2 containing Fe2+ and using hydrogen peroxide produced in situ by the reduction of oxygen at gas diffusion electrodes is demonstrated. It is shown that COD (chemical oxygen demand) of solutions containing such organics may be reduced by > 90% with a current efficiency > 50%, leading to acceptable energy consumptions.
University of Southampton
Harrington, Tomas Seosamh
1999
Harrington, Tomas Seosamh
Harrington, Tomas Seosamh
(1999)
Gas diffusion electrodes for environmental applications.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
A new type of uncatalysed gas diffusion electrode based on screen printing a C/PTFE mixture onto carbon fibre paper has been tested and studied for the reduction of oxygen to hydrogen peroxide. It is confirmed that hydrogen peroxide can be produced at a high rate in alkaline solution by the cathodic reduction of oxygen at an uncatalysed XC72-R carbon gas diffusion electrode For electrolyses carried out at constant current, in the range of 10-200 mA cm-2, the hydrogen peroxide concentration is seen to increase linearly with charge (to a limiting concentration of ~50mM). Moreover, the current efficiencies achievable are in excess of 90%. Voltammetry studies at each electrode in alkaline solution show iR drop to be distorting the responses.
The electrodes were applied successfully to the destruction of low levels of organics in synthetic aqueous effluents and media with pH between 1 and 3 were examined. In these acidic sulphate media, the effect of iR drop is shown to be more severe. The limitation, again, appears to be associated with an iR drop in the electrolyte within the pores of the carbon powder/PTFE active layer and this difficulty is magnified by the relatively low conductivity of the solutions used in this work. Oxygen is, however, reduced in these acid solutions and current densities of ~100 mA cm-2 can be reached. As the pH was decreased the current efficiency for hydrogen peroxide production appeared to drop but this results from chemical decomposition of hydrogen peroxide in homogeneous solution. Although hydrogen peroxide does not appear to be stable in the low acidity, the successful removal of several organics (phenol, aniline, acetic acid, formaldehyde and three azo-dyes) from aqueous solution at pH 2 containing Fe2+ and using hydrogen peroxide produced in situ by the reduction of oxygen at gas diffusion electrodes is demonstrated. It is shown that COD (chemical oxygen demand) of solutions containing such organics may be reduced by > 90% with a current efficiency > 50%, leading to acceptable energy consumptions.
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Published date: 1999
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Local EPrints ID: 463839
URI: http://eprints.soton.ac.uk/id/eprint/463839
PURE UUID: 80a2b74f-ce0b-4aa8-b1bb-1815926c20fe
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Date deposited: 04 Jul 2022 20:57
Last modified: 04 Jul 2022 20:57
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Author:
Tomas Seosamh Harrington
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