EFFECT OF INORGANIC CATIONS ON THE ELECTROREDUCTION OF NITRATE ANIONSON PT-VERTICAL-BAR-PT ELECTRODES IN SULFURIC-ACID-SOLUTIONS

It is shown that modification of the surface of Pt\Pt electrodes by ca tions Ni2+, Co2+, Cd2+, and Ge4+ accelerates the electroreduction of N O; anions in sulfuric acid solutions in the potential region close to a complete coverage of the surface by H-ads in the supporting electrol yte solution. The electrocatalytic effect of these surface modifiers i ncreases in the following sequence: Ge > Ni > Co approximate to Cd and also depends on the conditions of adsorption of the cations and nitra te anions. It is shown that Ge adatoms promote the NO; electroreductio n most efficiently when they occupy only a part of the electrode surfa ce, and the remaining part is occupied by adsorbed hydrogen. In the pr esence of Ni2+, Co2+ and Cd2+ cations, ammonium ions are detected as t he reaction product, while, in the presence of Ge adatoms, hydroxylami ne is also found among the reaction products. Suppositions are made ab out the possible causes of the electrocatalytic effects observed. (C) 1998 Elsevier Science S.A. All rights reserved.