MoV-MoVI mixed valence polyoxometalates for facile synthesis of stabilized metal nanoparticles:: Electrocatalytic oxidation of alcohols

Mo-V-Mo-VI mixed valence polyoxometalates (POMs), H-7[beta-P(Mo-V)(4)(Mo-VI)(8)O-40] (1), (NH4)(10)[(Mo-V)(4)(Mo-VI)(2)O-14(O3PCH2PO3)(2)(H2OPCH2PO3)(2)]center dot 15H(2)O (2), and [epsilon-P(Mo-V)(8)(Mo-VI)(4)O-36(OH)(4){La(H2O)(2.5)Cl-1.25}(4)]center dot 27H(2)O (3), respectively, were selected because they possess built-in reducing abilities. They were used for the synthesis of Pt-0 and Pd-0 nanoparticles (NPs) in water at room temperature without UV irradiation. Small size NPs (1.7-4 nm) were obtained, their stabilization following the order 1 > 2 > 3. They were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and electrochemistry. Detection of molybdenum in XPS and electrochemistry supports the hypothesis that each polyoxometalate serves both as a reductant and as a protective layer, in agreement with the propensity, particularly of Mo-based POMs, to self-assemble on metal and other solid surfaces. The Pt-0 and Pd-0 NPs were tested for the electrocatalytic oxidation of methanol and ethanol, respectively, and proved efficient for these processes. In addition, Pt-0 was resistant to poisoning during methanol oxidation. The synthesis of these stabilized nanoparticles is facile and provides materials that show promise for use in fuel cells.