Cu/CuxO and Pt nanoparticles supported on multi-walled carbon nanotubes as electrocatalysts for the reduction of nitrobenzene

Cu/CuxO and Pt nanoparticles supported on multi-walled carbon nanotubes (MWCNTs) were studied as electrocatalysts for the reduction of nitrobenzene in a half-cell set-up. This reaction not only produces valuable chemicals, but has the potential to generate electricity if applied in a fuel cell device. MWCNTs with and without functional groups were investigated as supports for the nanoparticles, employing either ethylene glycol (EG) or H2 gas as reductant. Cu/CuxO nanoparticles supported on pristine multi-walled carbon nanotubes prepared using H2 as reductant (Cu/MWCNT-H2) were identified as the best electrocatalyst for the reduction of nitrobenzene on the basis of its onset potential and of the number of electrons transferred per nitrobenzene molecule. This material consists of well-dispersed Cu/CuxO nanoparticles with an average size of 8 nm. The stability of Cu/MWCNT-H2 was tested by cyclic voltammetry (CV) for 1000 cycles, showing that the activity of this electrocatalyst does not deteriorate over time. The electrochemical reduction of nitrobenzene over Cu/MWCNT-H2 in acidic ethanolic medium at −0.62 V vs. Fc/Fc+ led to 44% conversion with an overall selectivity toward azoxybenzene (AOB) of 82%.