Ternary graphene-CoFe2O4/CdS nanohybrids: Preparation and application as recyclable photocatalysts

Graphene (Gr)-based binary Gr-CoFe₂O₄ and Gr-CdS or ternary Gr-CoFe₂O₄/CdS nanohybrids were prepared via a facile solvothermal strategy. It was encouraging to find that the ternary Gr-CoFe₂O₄/CdS nanohybrids exhibited the highest photocatalytic degradation ability (80%) among all the photocatalysts. The significant enhancement in photodegradation under 40 W daylight lamp irradiation was attributed to graphene acting as a "bridge", where electrons generated from CoFe₂O₄ were transferred to CdS by graphene and finally led to separation of electrons and holes. Interestingly, neat CoFe₂O₄ resulted in increasing concentration of methylene blue (MB) as the irradiation time increased. The phenomenon was ascribed to adsorption of MB molecules on CoFe₂O₄ in the dark and desorption from the photocatalyst during irradiation, confirmed by our ingenious experiment. Digital photos of the Gr-CoFe₂O₄/CdS hybrids in an external magnetic field indicated that the ternary photocatalyst could be easily separated from aqueous solution. The recycle measurements of the photocatalyst revealed that the ternary nanohybrids exhibited acceptable photocatalytic stability due to unstable decoration. This work would provide a new insight into the construction of visible light-responsive and magnetic separable photocatalysts with high performances. © 2013 The Royal Society of Chemistry.