MoV−MoVI Mixed Valence Polyoxometalates for Facile Synthesis of Stabilized Metal Nanoparticles: Electrocatalytic Oxidation of Alcohols

High Resolution Image Download MS PowerPoint Slide Mo V −Mo VI mixed valence polyoxometalates (POMs), H 7 [β-P(Mo V ) 4 (Mo VI ) 8 O 40 ] ( 1 ), (NH 4 ) 10 [(Mo V ) 4 (Mo VI ) 2 O 14 (O 3 PCH 2 PO 3 ) 2 (H 2 OPCH 2 PO 3 ) 2 ]·15H 2 O ( 2 ), and [ε-P(Mo V ) 8 (Mo VI ) 4 O 36 (OH) 4 {La(H 2 O) 2.5 Cl 1.25 } 4 ]·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.