Doping nano-Co3O4 surface with bigger nanosized Ag and its photocatalytic properties for visible light photodegradation of organic dyes

This paper reports the synthesis of nanosized Ag/Co 3 O 4 composite catalysts using a silver-mirror reaction and the calibration of their catalytic activities towards methyl blue (MB) dye degradation with peroxymonosulfate (PMS) under visible light. The nanosized Ag/Co 3 O 4 composites were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV–vis spectroscopy. The experimental evidence indicated that the hydrothermal synthesis approach lead to the exposure of the {1   1   2} facets of the Co 3 O 4 nanoflakes. Compared to Co 3 O 4 nanoflakes, Co 3 O 4 doped with Ag nanoparticle (average diameters of 10–15   nm) presented lower band gap energy and photoluminescent (PL) intensity. Meanwhile, the Ag/Co 3 O 4 exhibited high stability and excellent dispersion property in dye solution. Experimental data suggested that 3.06   wt% Ag nanoparticle-doped Ag/Co 3 O 4 nanocomposite catalyst possessed the highest catalytic activity towards MB degradation in aqueous solution at the tested concentration level of 15   mg/L, about 2.4 times higher than that of pure Co 3 O 4 . Complete decolorization of the 15   mg/L MB solution can be achieved by 3.06   wt% Ag-doped Ag/Co 3 O 4 nanocomposite within 20   min of visible light irradiation.