A newly-designed polyoxometalate (POM)-based plasmonic visible-light catalyst, Ag/AgxH4-xSiW12O40 (Ag/AgHSiW) nanoparticles (NPs), is prepared by a green photoreduction strategy without the addition of any surfactant. The Ag/AgHSiW NPs, which possess abundant hydroxyl (OH) groups on their surface, has not only significantly enhanced visible spectrum absorption but also reduced photoluminescence (PL) emission. Compared with P25, Ag NPs, H4SiW12O40 (HSiW) and Ag4SiW12O40 (AgSiW), the Ag/AgHSiW photocatalyst shows high photocatalytic activity and stability for the decomposition of methyl blue (MB) under visible light irradiation, which could be attributed to highly synergic effect of photoexcited AgHSiW and plasmon-excited Ag NPs. (C) 2013 Elsevier B.V. All rights reserved.