Controlled synthesis of Pd–Ag nanowire networks with high-density defects as highly efficient electrocatalysts for methanol oxidation reaction

Abstract

Pd–Ag bimetallic catalysts containing different molar ratios of Pd/Ag (30/70, 50/50, and 70/30) were prepared using a facile visible-light-assisted liquid-phase method. The samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, high-resolution transmission electron microscopy, high-angle annular dark-field scanning transmission electron microscopy, selected-area electron diffraction, and inductively coupled plasma optical emission spectroscopy. Cyclic voltammetry and chronoamperometry measurements were used to evaluate their electrocatalytic properties toward the methanol oxidation reaction (MOR) in alkaline media. The alloyed Pd50Ag50 nanowire network with the optimized molar ratio, which had abundant defects (grain boundaries, lattice dislocations, lattice expansion, and distortion), provided more active sites for the MOR under alkaline conditions. The onset potential of the MOR on the Pd50Ag50-loaded glassy carbon electrode (GCE) was more negative than those on the Pd30Ag70, Pd70Ag30, and pure Pd electrodes. The Pd50Ag50 catalyst showed the best catalytic activity (2853 mA mgPd−1/6.85 mA cmPd−2) compared with those of the pure Pd catalyst (320 mA mgPd−1/2.68 mA cmPd−2) and other samples. This sample also exhibited a high tolerance (ib/if = 0.19) to the poisoning species and long stability (only lost 7.64 % after 500 cycles). The alloyed Pd50Ag50 network is a promising catalyst for the MOR. This work may be extended to construct advanced Pd–M (M = other metals) catalysts for fuel cell applications by surface defect engineering.