Effect of inorganic cations on the electroreduction of nitrate anions on Pt|Pt electrodes in sulfuric acid solutions

It is shown that modification of the surface of Pt\Pt electrodes by cations Ni2+, Co2+, Cd2+, and Ge4+ accelerates the electroreduction of NO; anions in sulfuric acid solutions in the potential region close to a complete coverage of the surface by H-ads in the supporting electrolyte solution. The electrocatalytic effect of these surface modifiers increases in the following sequence: Ge > Ni > Co approximate to Cd and also depends on the conditions of adsorption of the cations and nitrate anions. It is shown that Ge adatoms promote the NO; electroreduction most efficiently when they occupy only a part of the electrode surface, and the remaining part is occupied by adsorbed hydrogen. In the presence of Ni2+, Co2+ and Cd2+ cations, ammonium ions are detected as the reaction product, while, in the presence of Ge adatoms, hydroxylamine is also found among the reaction products. Suppositions are made about the possible causes of the electrocatalytic effects observed. (C) 1998 Elsevier Science S.A. All rights reserved.