Catalytic reduction of 4-nitrophenol and photocatalytic degradation of organic pollutants in water by copper oxide nanosheets

Self-assembly of metal oxide nanoparticles into two dimensional nanostructures has emerged as a promising strategy to fabricate efficient catalysts and photocatalysts for purification of water. Nanosheets of CuO were prepared using a simple wet chemical route using polyvinyl alcohol as a capping agent and investigated as catalysts for reducing 4-nitrophenol (4-NP) into 4-aminophenol (4-AP) and as photocatalysts for removal of methylene blue (MB) and methyl orange (MO) from water. Field emission scanning electron microscopy studies revealed nanosheets, which were found to be of monoclinic CuO from X-ray diffraction studies. The optical, catalytic and photocatalytic studies of the prepared CuO nanostructures were carried out by UV-visible absorption spectroscopy. The synthesized CuO nanosheets led to complete catalytic conversion of harmful 4-NP into very useful 4-AP by borohydride in just 5 min and photocatalytically degraded MB and MO in 160 and 180 min, respectively. The roles of active species in the photocatalytic process have been studied using different scavengers and the tentative mechanisms underlying the growth, photocatalytic and enhanced catalytic activities of CuO nanosheets were proposed.