Electrochemical Generation of Nitrogen Dioxide for Testing of Gas Sensors
UNESCO Laboratory of Environmental Electrochemistry, Department of Analytical Chemistry, Charles University, Prague
The generation of NO2 in a simple generator is based on galvanostatic reduction of nitrate anion to nitrite on silver cathode. Nitrite anion is chemically reduced directly in the generation solution with hydroquinone to nitrogen oxide. NO is oxidized in a stream of air to NO2 by passage through an oxidation column containing CrO3. The NO2 production is linearly dependent on generation current in a certain range of currents which depends on the cathode surface area. The production is stable for at least six hours. Due to a low electrolytic efficiency (about 4.5 %), the NO2 production cannot be calculated from Faraday law but must be determined experimentally.
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