The electrocatalytic behaviour of Pt and Cu nanoparticles supported on carbon nanotubes for the nitrobenzene reduction in ethanol

In view of investigating the possibility of cogeneration of chemicals and electricity in a fuel cell type reactor, a suitable electrocatalyst and optimal reaction conditions have to be found. The nitrobenzene reduction was taken as the case study reaction for this investigation. In literature no suitable electrocatalyst has been found for this reaction. Pt and Cu nanoparticles, supported by multiple wall carbon nanotubes, were taken as electrocatalysts and ethanolic and acidic ethanolic environments were studied as possible reaction media. The Cu nanoparticle catalyst displayed superior electrocatalytic behaviour since less overpotential is needed for the nitrobenzene reduction in both ethanolic and acidic ethanolic environment. The acidic ethanolic conditions were superior to the ethanolic conditions as less overpotential was required for the nitrobenzene reduction reaction and a higher conversion of nitrobenzene is obtained. In acidic ethanolic environment, a four-electron reduction is taking place, which was assigned to the reduction of nitrobenzene into phenylhydroxylamine. This compound is re-oxidised into nitrosobenzene when the solution comes into contact with oxygen, and the formed nitrosobenzene selectively reacts with another phenylhydroxylamine molecule, yielding azoxybenzene. The latter is an important compound in organic synthesis.