The influence of copper in dealloyed binary platinum-copper electrocatalysts on methanol electroxidation catalytic activities

In this study, we prepared and characterized carbon paper-supported dealloyed binary Pt-Cu core-shell electrocatalysts (denoted as Pt_xCu_(100-x)/CP) by cyclic co-electrodeposition and selective copper dealloying in an acidic medium, and we investigated the effect of the copper content in the samples on the catalytic activities toward methanol electroxidation reaction (MOR). X-ray photo-emission spectroscopy (XPS) and inductively coupled plasma atomic emission spectroscopy (ICP-AES) indicated that the structure of dealloyed binary Pt-Cu catalysts possessed a Pt-rich shell and a Cu rich core. X-ray absorption near edge spectroscopy (XANES) displayed that the oxidation states of Pt and Cu were zero and one, respectively, implying the formation of metallic Pt and Cu₂O, respectively. X-ray diffraction spectroscopy (XRD) confirmed that Cu was inserted into a face-centered cubic Pt structure forming Pt-Cu alloys. Scanning electron microscopy (SEM) and transmission electron microscope (TEM) displayed a cubic shape of Pt/CP and a spherical shape of Pt_xCu_(100-x)/CP with several hundred nanometer sizes of agglomeration that depended on the Cu content. Cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy were performed to confirm that the sample of Pt₇₀Cu₃₀/CP exhibited the best catalytic activities in terms of the specific current, current density, catalytic poisoning tolerance, and stability.