ELECTROCHEMISTRY OF NITRIC OXIDE AND OF NITROUS ACID AT A MERCURY ELECTRODE

The electrochemistry of nitric oxide and nitrous acid have been studied at a mercury electrode in buffered aqueous solutions using chronopotentiometry and controlled-potential coulmetry. The reduction of NO is an irreversible one-electron process with αna=0.40 and ks, h=10-. Gas chromatographic analyses establish that the only product is N2O. The electroactive species appears to be a slowly formed intermediate, HNO+, with a formation constant of 107. Nitrous acid is irreversibly reduced at a memory electrode by a one-electron process, the kinetic parameters for the rate-controlling electron transfer step having the values αna=0.49 and ks, h-107 cm sec-1. The electroactive species appears to be a rapidly formed intermediate, H2NO2+. Controlled-potential coulometry for the reduction of nitrous acid indicates an overall three-electron process (at pH 3.00). Gas chromatography establishes that the major products are equivalent amounts of NH2OH and N2O. The actual electrochemical reduction of HNO2 is an overall four-electron process to give NH2OH which reacts with HNO2 to give N2O. MEchanisms consistent with the experimental data are proposed for the reduction of NO and of HNO2. © 1968.