Electrocatalytic reduction of nitrate and nitrite to hydroxylamine and ammonia using metal cyclams

摘要: Abstract Co(III)-cyclam (cyclam = 1,4,8,11-tetra-azacyclotetradecane) has been demonstrated to act as a new and excellent catalyst for NO − 3 2 reduction by cyclic voltammetry controlled-potential electrolysis (CPE). CPE of KNO solution at an Hg electrode gave hydroxylamine selectively with high current yields (ca. 90%); the densities were > 5 mA/cm in 0.1 M −1.5 V (vs. SCE) presence only 20 μ or less catalyst. The turnover frequency was 500 h −1 (using 8 cm pool electrode), no deactivation observed after several hours. At Ag, Cu Pb electrodes, reduced further give ammonia preferentially. Ni(II)-cyclam also acted catalyst, but effective potential region ca. 0.2 more negative than that Co(III)-cyclam. Some mechanistic investigations suggested formation Co(I)- Ni(I)-cyclam, which adsorbed onto surface, would be effective, role cyclam ligand provide sufficient nucleophilicity catalysts and/or suitable structure interaction nitrogen oxyanions.