Hollow Pt/Ag composite nanospheres, which show highly enhanced catalytic properties, have been prepared through a galvanic replacement reaction of silver nanoparticles dispersed in Ptn+-added water. Ptn+, prepared in advance by the partial reduction of Pt4+ with weak reducing agents, is readily reduced galvanically to form porous Pt shells, and concomitantly produced Ag+ diffuses out to produce hollow Pt/Ag nanocomposites finally. The residual silver has been further eliminated from the composites with 0.5 M HNO3(aq) to produce hollow Pt nanospheres. Hollow Pt/Ag composite nanostructures have been found to catalyze the degradation of rhodamine B efficiently in the presence of KBH4, although their catalytic performances depend highly on the metals, sizes, and shapes of the nanostructures. (C) 2011 Elsevier B.V. All rights reserved.