Synthesis of Cu2O microcubes for facet selective reduction of 4-nitrophenol

Nanomaterials with enhanced active sites are essential for improving the catalytic activity of nanomaterials. Herein, we report a simple and one-step hydrothermal method to synthesize highly active catalytic Cu2O microcubes in aqueous phase using sodium citrate in the presence of cetyl trimethylammonium bromide (CTAB) as a cationic surfactant. The electron microscopy investigations revealed the formation of sharp edged uniformly distributed Cu2O microcubes of 2.5 +/- 0.5 mu m in size. The Cu2O crystal model showed (100) plane having oxygen atoms in the unit cell and Cu atoms as dangling bonds with subsequent (111) plane that resulted in excess positive charge on the cubic surface. A detailed investigations on {110} and {111} facets revealed that the {110} facet had similar to 1.5 times more Cu atoms than the {111} facet. The formed Cu2O microcubes showed enhanced catalytic activity for converting p-nitrophenol into p-aminophenol. The reaction followed a linear trend at different catalyst concentrations and their rate constants and conversion time were estimated. The {110} and {111} facets acted as predominant active sites for the catalytic conversion, most likely the positive charge resulted by the dangling Cu atoms enhanced the adsorption of hydride ions. Hence, the proposed microcube system have huge potential in areas such as microreactors, photovoltaics, electronics, optics and biosensing.

Automated summary

A simple and one-step hydrothermal method was developed to synthesize highly active catalytic Cu2O microcubes, and their catalytic activity for converting p-nitrophenol into p-aminophenol was investigated. The results showed that the formed Cu2O microcubes exhibited enhanced catalytic activity, and the {110} and {111} facets were identified as the predominant active sites. The positive charge resulted from the dangling Cu atoms on the {110} and {111} facets enhanced the adsorption of hydride ions.