Core-shell structured reduced graphene oxide wrapped magnetically separable rGO@CuZnO@Fe^sub 3^O^sub 4^ microspheres as superior photocatalyst for CO^sub 2^ reduction under visible light

A highly efficient, recyclable and magnetically separable core-shell structured CuZnO@Fe3O4 microsphere wrapped with reduced graphene oxide (rGO@CuZnO@Fe3O4) photocatalyst has been developed and used for the photoreduction of carbon dioxide with water to produce methanol under visible light irradiation. Owing to the synergistic effect of the components and to the presence of a thin Fe2O3 layer on Fe3O4, rGO@CuZnO@Fe3O4 4 exhibited higher catalytic activity as compared to the other possible combinations such as CuZnO@Fe3O4 2 and GO@CuZnO@Fe3O4 3 microspheres. The yield of methanol in case of using 2 and 3 as photocatalyst was found to be 858 and 1749 µmol g-1 cat, respectively. However, the yield was increased to 2656 µmol g-1 cat when rGO@CuZnO@Fe3O4 4 was used as photocatalyst under similar experimental conditions. This superior photocatalytic activity of 4 was assumed to be due to the restoration of the sp2=2 hybridized aromatic system in rGO, which facilitated the movement of electrons and resulted in better charge separation. The synthesized heterogeneous photocatalyst could readily be recovered by external magnet and successfully reused for six subsequent cycles without significant loss in the product yield.