Proper alloying of Pt with underlying Ag nanoparticles leads to dramatic activity enhancement of Pt electrocatalyst

Nanostructures containing Pt-flecks on Ag colloids (Pt^Ag) were prepared by Pt deposition from citrate reduction of PtIVCl62- or PtIICl42- ions. The nanostructures prepared from PtIVCl62- showed more or less Pt–Ag alloying due to the galvanic replacement reaction between PtIVCl62- and metallic Ag colloids. The Pt–Ag alloying at the surface of Ag colloids was manipulated by tuning the atomic Pt/Ag ratio (m) during preparation. It was demonstrated that a proper Pt–Ag alloying in a narrow composition window (0.47 ⩽ m ⩾ 0.53) can led to a dramatic activity enhancement of Pt, up to one order of magnitude higher, for methanol electro-oxidation.