Influence of oxidative treatment of copper grid electrodes on the efficiency of conversion to aniline in the electroreduction of nitrobenzene and azobenzene in basic aqueous methanol

Abstract

The influence of preoxidizing the surface of polycrystalline copper electrodes on the efficiency of the controlled potential electrochemical reduction of nitrobenzene and azobenzene to aniline in basic aqueous methanol has been investigated. Electrodes electrochemically preoxidized to CU(OH)~ or to CuzO gave high yields of aniline (90-100%) with high current efficiencies (88-99%) for the electrohydrogenation of nitrobenzene compared to electrodes preoxidized by air (7-29% of aniline, 64-74% current efficiency). For the electrohydrogenation of azobenzene, copper electrodes preoxidized to CuzO were found to be more active (average yield of aniline of 28%, average current efficiency of 55%) than electrodes preoxidized to CU(OH)~ (3-1 1% of aniline, 42-53% current efficiency), and electrodes preoxidized by air were inactive (the electrohydrogenation stopped at hydrazobenzene). The improvement of activity induced by preoxidation of the copper surface is linked to the increase of the surface area.

Surface-Enhanced Raman Spectroscopy of Phosphate Anions: Adsorption on Silver, Gold, and Copper Electrodes

“…In solution II, the pair of anodic and cathodic peaks located in the potential region -0.1 to -0.3 V (Figure 6a, CV insert) are related with the formation and reduction of the Cu(I) species (solid Cu 2 O and soluble Cu(I)), as has been established by voltammetric, X-ray diffraction, and ellipsometric investigations of others. [25][26][27][28] In the SER spectra, only features related with Cu oxide and adsorbed OHions were observed at electrode potentials that were more positive than about -0.4 V (Figure 6a). Several broad peaks appear in the region of 400-600 cm -1 in the spectra obtained at -0.2 V and at potentials more positive than the voltammetric reduction peak.…”

Polyaniline films containing palladium microparticles for electrocatalytic purposes

“…The hydrogenation of NBA was chosen to test the catalytic activity of PAni-Pd cathodes prepared under the It is well known that at catalytically active electrodes, such as Devarda copper [45] or Raney nickel [46], nitrobenzene can be reduced to aniline with good yields. For the conversion of nitrobenzene to phenyl hydroxylamine an electronation-protonation mechanism is widely accepted; further reduction to aniline is often considered to involve an electrocatalytic hydrogenation [47].…”