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.
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