Highly Efficient Cuprous Oxide Nanocrystals Assisted with Graphene for Decolorization Using Visible Light

The preparation of rhombic dodecahedral cuprous oxide (rdCu₂O) decorated with various amounts of reduced graphene oxide (rGO) is carried out by using a wet-chemical route. The resultant nanocomposites (denoted as rdCu₂O-xrGO, x = amounts of rGO) possess unique crystal facets of Cu₂O and superior electronic properties of rGO, which are tested as photocatalysts in the degradation of methyl orange (MO) under visible light irradiation. Among all the rdCu₂O-xrGO photocatalysts, the rdCu₂O-1rGO is found to degrade ca. 98% of MO in the presence of very low catalyst concentration (0.0625 g L⁻¹) within 120 min under visible light illumination. This obtained result may be owing to the well interfacial contact of rhombic dodecahedral Cu₂O nanoparticles with high electronic conductivity of rGO sheets that can increase the separation of photo-induced electron-hole pairs, stabilize the Cu₂O, and enhance MO adsorption, which are proofed by using X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, photoluminescence, and UV-Vis diffuse reflection spectroscopy. Most importantly, these efficient photocatalysts can be reusable and retain surpassing photoactivity in terms of MO degradation after cyclic tests, which may provide a possible opportunity for practical applications in purifying wastewater via direct sunlight.