High performance of Pd and PdAg with well-defined facets in direct ethylene glycol microfluidic fuel cells

The development of bimetallic nanomaterials with well-defined facets is highly desired in electrocatalysis to improve the alcohols oxidation. In this work, PdAg nanoparticles containing abundance of (100) facets and Pd nanocubes enclosed within (100) facets as control are synthesized and used as electrocatalysts towards ethylene glycol oxidation in alkaline medium. Transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HR-TEM) reveal that PdAg is composed by semispherical and semi-cubic nanoparticles with average sizes of 4.1 +/- 0.45 nm; Pd shows a well-defined nanocubes shape with particles sizes of 9.9 0.53 nm. X-ray diffraction and X-ray photoelectron spectroscopy (XPS) confirm the presence of Pd-0 in the PdAg material. Elemental mapping analysis of PdAg/C material at different electrochemical cycles indicates that PdAg has an atomic composition of Pd30Ag70, and it is maintained during the electrochemical experiments. The presence of (100) facets and silver in the PdAg electrocatalyst improves the EGOR activity; decreasing the onset potential and improving current density and stability. Microfluidic fuel cell evaluation shows higher cell voltage (0.71 V) for PdAg in comparison to Pd nanocubes (0.51 V), presenting similar power densities (5.2 mW cm(-2)) despite PdAg uses 2.6 lower Pd loading, and it has high stability in a pH-dual electrolyte configuration. (C) 2019 Elsevier Ltd. All rights reserved.