Publikationsserver der RWTH Aachen University
Zur elektrochemischen Oxidation des Ammoniak
Abstract
dc:descriptionConsidering the limited availability of fossile energy resources the fuel cell (FC) concept is of increasing importance. In this work the suitability of ammonium for usage in a PEMFC has been studied. A commercialy available PEMFC (H-Tec) has been utilized in conjunction with hydrogen on one hand and compared to the utilization of ammonium on the other hand. Hydrogen yielded a stable clamp voltage of 0.9 volts, whereas the clamp voltage broke down to 0.05 volts within 20 minutes in the ammonium case. Further experiments have shown the damage of the FC by ammonium. The reusage of hydrogen lead to overall cell voltage of only 0.4 to 0.5 volts. Another option for utilizing ammonium as a carrier of energy is electrochemical decomposition which has also been investigated. cyclovoltammograms of ammonium in aprotic solvents with platinum, palladium, gold, graphit, steel, zink, titanium, and copper electrodes have been measured. Compared to other materials platinum, palladium, and gold are advantegous due to their low ammonium oxidation potential of approximately 1.0 volt. Further investigations with rotating disk electrodes produced no reliable results due to fast ammonium depletion by the electrode thus limiting current measurements. It is well known that the electrochemical oxidation is effected by nitrogen adsorption at the electrodes. Some mediators such as Mn(II)/Mn(III), Cu(I)/Cu(II) or 2,2,6,6-Tetrametyl-piperidinyl-1-oxyl-Radikal (TEMPO) have been studied by CV for their ability to prevent this effect. Only for TEMPO a positive effect on the ammonium oxidation could be observed. According to the measurements a mechanism has been postulated. The performance of electrolyses may be expressed in terms of the energy balance meaning the difference of energy retrievable from the hydrogen fuel cell and that consumed by the ammonium oxidation. We observed negative energy balance for ammonium solution with TEMPO whereas by applying the ammonia gas to the inside of the electrode we achieved positive energy balance in the ammonium solution case for about 15 minutes.
Degree
thesis:*- Grantor dc:publisher
- Publikationsserver der RWTH Aachen University
- Year dc:date
- 2003
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- Repges, Arndt
- Contributors dc:contributor
-
- Thomas, Hans Günter
Subjects
dc:subject × 7Rights
dc:rights- Statement dc:rights
-
- info:eu-repo/semantics/openAccess
- Language dc:language
- ger