The accelerating effect of silver ion on the degradation of methyl orange in Cu2O system

In this paper we reported an interesting phenomenon that additive Ag+ ion can rapidly and continuously capture the activated electrons which accumulated on the surface of as-prepared Cu2O catalyst, resulting in residual holes directly and rapidly reacting with methyl orange (MO) to be degraded. When 10(-2) M Ag+ was added rapidly into the suspension containing 800 mg/L MO, the decolorizing rate immediately reached 38%, and rapidly increased to 88% in 30 min. This accelerating effect of Ag+ ion on MO degradation was first observed in Cu2O system. Although the as-prepared Cu2O shows a very large particle size (similar to 2.2 mu m), it possesses loose crystal structure with rough multiple surfaces and various defect levels in the interior and on the surface to promote the massive accumulation and fast migration of electron and hole. As a result, when Ag+ ion was added into the suspension, it immediately reacted with the accumulated electron to turn into metallic Ag and deposited on the surface of Cu2O to form a core-shell structured catalyst Cu2O@Ag, resulting in fast degradation of MO via directly reacting with residual hole. The Schottky barriers which generate at the junctions of Cu2O and metallic Ag crystals can speed up the directional migration of electron and hole, resulting in effective separation of electron-hole pair. In addition, Cu2O@Ag catalyst shows strong light absorption in UV, vis and NIR region. These results indicate that the as-prepared Cu2O catalyst exhibits a very high photocatalytic activity in the case of adding high concentration Ag+ ion. (C) 2015 Elsevier B.V. All rights reserved.