Electrochemical Generation of Nitrogen Dioxide for Testing of Gas Sensors

Abstract

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.