Construction of Pt-Ni nanocomposites from Pt-Ni multinuclear complexes on gold(111) surface and their electrocatalytic activity for methanol oxidation

Abstract

Novel electrocatalysts for methanol oxidation were prepared from two Pt-Ni multinuclear complexes, [Pt2{Ni(NH2CH2CH2S)2}4]Cl4 and [Pt(bpy){Ni(NH2CH2CH2S)2(bpy)}](NO3)2 (bpy=2,2′-bipyridine). They were adsorbed on a Au(111) surface by immersing the Au(111) electrode in solutions containing these complexes. The modified Au(111) electrodes were then subjected to potential cycling or heat-treatment at 200°C and 300°C so that organic ligands were decomposed and adsorbed complexes were converted to nanocomposites. For a comparison, Au(111) electrode modified by a Pt based nanocomposite prepared by using a di-platinum(II) complex ([Pt2(terpy)2(μ-otdst)]2+ (terpy=2.2′:6′,2″-terpyridine, H2otdst=2-octylthio-4,6-disulfanyl-1,3,5-triazine)) as a starting molecule. The surface species were characterized by X-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM) in addition to cyclic voltammetry (CV). Two-dimensional nanocomposites of monatomic height were observed by STM. The coverages of the nanocomposites were 2–8%. By repeating the complex adsorption and heat-treatment for five times, nanocomposites of higher coverage of 13–19% with monatomic height were formed on Au(111) surface. The resultant nanocomposites showed high activity for methanol oxidation reaction (MOR) with an improved CO-tolerance in a 0.1M KOH aqueous solution containing 1M CH3OH.