Photocatalytic hydrogenation of nitroarenes: supporting effect of CoOx on TiO2 nanoparticles

Abstract

Cobalt oxide visible light-active photo-catalysts supported on TiO₂ nanoparticles with varying amount of cobalt oxide [3% CoO_x/TiO₂ (A), 4% CoO_x/TiO₂ (B), 5% CoO_x/TiO₂ (C)] were synthesized by solid-state method followed by calcination. The as-synthesized catalysts were characterized by various techniques such as powder XRD, TEM, EDX, UV-Vis-DRS and XPS analysis. The photocatalytic activity of the as-synthesized materials was studied for the reduction of nitroarenes to the corresponding amines using hydrazine monohydrate as the reductant. Cobalt(II) oxide is responsible for the reduction of nitroarenes and then, cobalt(III) is reduced back to the original compound by hydrazine hydrate, thus ascertaining the catalytic nature of this hydrogenation process. XPS suggests the presence of Co(II) in CoO_x/TiO₂.