Pt-Cu electrocatalysts for methanol oxidation prepared by partial galvanic replacement of Cu/carbon powder precursors

A bimetallic Pt-Cu carbon-supported catalyst (Pt(Cu)/C) has been prepared by a room temperature two-step procedure involving the chemical reduction of Cu ions by sodium borohydride in the presence of Vulcan XC72R carbon powder, followed by the partial galvanic replacement of Cu particle layers by Pt, upon immersion in a chloroplatinate solution. The characterization of the Pt(Cu)/C catalyst by XRD has proven the formation of a Pt–Cu alloy while cyclic voltammetry in deaerated acid revealed similar characteristics to those of pure Pt. These two findings point to the existence of Pt-rich outer layers and a Pt–Cu core. The electrocatalytic activity of the bimetallic Pt(Cu)/C catalyst towards methanol oxidation is comparable to or better than that of a commercial 20% Pt Vulcan XC72R catalyst (when assessed by voltammetric or prolonged chronoamperometric experiments respectively). This is attributed to the effect of Cu on CO poison adsorption and removal from Pt. Moreover, related to the same effect but also to the reduced Pt loading of the mixed Pt–Cu particles, the specific mass activity of the prepared catalyst is superior to that of the commercial catalyst.

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► Bimetallic Pt–Cu nanoparticles, supported on fuel cell technology carbon supports, have been prepared by a combination of Cu chemical reduction followed by its partial galvanic replacement by Pt.
► The formation of a Pt–Cu alloy was confirmed by XRD whereas voltammetry points to the existence of a Pt-rich shell.
► The prepared Pt-Cu/C catalysts exhibited moderately enhanced catalytic activity for methanol electrooxidation in acid and significantly better Pt utilization.