Preparation, Characterization and Properties of Pt-Cu Co-reduced and Pt-on-Cu Skin Type Bimetallic Carbon-Supported (Vulcan XC72) Electrocatalysts

Abstract

Pt/Cu salt co-reduction and, subsequent reduction of Cu(acac)2 and PtCl2 allows to generate either alloyed Pt-Cu or skin type Pt-on-Cu carbon-supported (20 wt%, Pt:Cu = 50:50 a/o on Vulcan XC72) electrocatalysts. An examination by TEM revealed that the co-reduced Pt-Cu catalyst have well dispersed bimetallic nanoparticles (av. particle size 3.6 nm). The skin type Pt-on-Cu catalyst shows tiny Pt clusters (1-2 nm) decorating the surface of larger Cu particles (6-8 nm). XRD pattern of the co-reduced Pt-Cu catalyst shows weak and broad diffraction peaks consistent with a predominantly alloyed composition (plus a few Pt crystallites). Pattern of the skin type Pt-on-Cu/C catalyst reveals larger nanoparticles and points to the formation of (surface) alloy. SEM/EDAX showed a uniform metal distribution present in both Pt-Cu systems. XPS measurements indicated that in both cases only Pto is present. In co-reduced alloy catalyst a higher amount of Cu2+ was present at the nanoparticle surface (Cuo/ Cu2+ = 0.6), while on the surface of the skin type Pt-on-Cu system Cuo and Cu2+ exist in equal amounts (Cuo/ Cu2+ = 1.0). Both types of Cu containing catalysts have higher mass specific activity in hydrogen oxidation reaction (HOR) than the industrial benchmark Pt/C catalyst. The electrocatalytic properties depend on morphological structure subtleties