Engineering the Cu2O–reduced graphene oxide interface to enhance photocatalytic degradation of organic pollutants under visible light

In this work, Cu2O–reduced graphene oxide (rGO) composites were synthesized with tunable Cu2O crystal facets ({1 1 1}, {1 1 0} and {1 0 0} facets). The degradation performance of methylene blue under visible light was ranked: o-Cu2O{1 1 1}–rGO > d-Cu2O{1 1 0}–rGO > c-Cu2O{1 0 0}–rGO. UV–vis diffuse reflectance and photoluminescence spectra showed that o-Cu2O–rGO exhibited the enhanced visible-light absorption and the faster charge-transfer rate. Furthermore, X-ray photoelectron spectroscopy and Raman characterizations showed that o-Cu2O–rGO was beneficial for the stabilization of Cu+ species and the formation of oxygen defects. With the help of in-situ electron spin resonance (ESR), more superoxide radicals were detected over o-Cu2O–rGO, which promoted organic pollutants degradation. The above results confirmed that the catalytic behaviors of three Cu2O–rGO composites were related to the electronic structures and interfacial connections. The o-Cu2O{1 1 1}–rGO displayed the superior performance, for the highly-active coordinated unsaturated Cu and the intensive interfacial connection, which was beneficial for the rapid the photo-generated electron transfer and the formed active superoxide species. This study showed that engineering the interfacial structures could provide a scientific basis for the design of efficient photo-catalysts.