Synchronous synthesis of Cu₂O/Cu/rGO@carbon nanomaterials photocatalysts via the sodium alginate hydrogel template method for visible light photocatalytic degradation

A series of Cu₂O/Cu/rGO@carbon nanomaterial (Cu₂O/Cu/rGO@CN) heterogeneous photocatalysts were successfully synthesized synchronously via a novel sodium alginate hydrogel method. Cu₂O nanoparticles (~50nm) were synthesized by calcination under the protection of a nitrogen atmosphere. Cu nanoparticles (~6nm) inevitably appeared on the surface of Cu₂O, thereby forming a Cu₂O/Cu heterostructure which is known as a Schottky junction. Graphene oxide (GO) nanosheets were synchronously reduced in situ by sodium alginate during the synthesis process and eventually acted as a 3-D structure with the assistance of the hydrogel skeleton. Because of the 3-D rGO modification, both the adsorption capacity and the photocatalytic activity of Cu₂O/Cu/rGO@CN were significantly improved. The rate of p-nitrochlorobenzene (p-NCB) degradation catalyzed by Cu₂O/Cu/rGO@CN was ~1.97×10^-2min^-1, which was much higher than that of the degradation catalyzed by Cu₂O/Cu@CN (~0.239×10^-2min^-1). This result could be attributed to the two-stage Cu₂O/Cu/rGO heterostructure, which facilitated efficient electron-hole separation. This method has the advantages of nontoxic raw materials, facile synthesis and reduced auxiliary usage, providing a new technique for designing heterogeneous photocatalysts.