Gold–Mediated Enhancement of Methanol Oxidation Activity and Selectivity on Pt–Au@Ni Electrocatalysts

The methanol electrooxidation reaction (MOR) on mixed-metal electrocatalysts has drawn tremendous interest as a means to improve the catalytic efficiency and product selectivity. Herein, bifunctional Pt–Au@Ni catalysts formed through galvanic exchange are shown to exhibit high catalytic activity toward MOR. Voltammetric responses of MOR on Pt–Au@Ni and Pt@Ni catalysts exhibit characteristics of Ni-catalyzed MOR at high overpotentials and Pt-catalyzed MOR at low overpotentials but with a significantly higher current density on a per-surface Pt atom basis compared to a Pt electrode. In situ surface-enhanced infrared absorption spectroscopy (SEIRAS) measurements reveal that Pt–Au@Ni promotes selective conversion of methanol to formate on Pt sites with greatly suppressed CO formation while increasing the formate to carbonate product ratio on Ni sites. Favorable effects of composition engineering on the electronic structures of the materials, which are assessed by using XPS, are evoked to rationalize the greatly enhanced intrinsic activity of Pt sites in the Pt–Au@Ni catalyst. The enhancement is linked to alteration of the electronic structure of Pt by addition of Au and Ni leading to improved metal–reactant/intermediate interaction energies, in accordance with the Sabatier principle.