High Performance Ag Rich Pd-Ag Bimetallic Electrocatalyst for Ethylene Glycol Oxidation in Alkaline Media

Efficient electrocatalysts at decreasing cost for ethylene glycol (EG) oxidation reaction are highly demanded for generating electricity out of direct EG fuel cells and producing hydrogen from EG electroreforming cells. In this work, carbon-supported Pd-Ag bimetallic catalysts (Pd x Ag y /C) with varying atomic ratios (x: y = 2: 1, 1: 1, 1: 2, 1: 3 and 1: 4) are synthesized by adding a Pd(II) precursor solution in a preformed Ag colloid in the presence of ascorbic acid followed by mixing with carbon black, and then are screened for EG electrooxidation in alkaline media. ICP-AES, TEM, XRD and XPS are used to characterize the obtained Pd x Ag y /C catalysts. The resulting Pd x Ag y nanoparticles exhibit similarly mean sizes of ca. 9.5 nm and an essentially alloy structure with a Pd surface enrichment rather than a typical Ag core-Pd shell structure. Electrocatalytic evaluation reveals that the as-synthesized Pd x Ag y /C catalysts display a "volcano" profile in terms of the Pd mass activity with increasing y: x value, and the Pd 1 Ag 3 /C yields the most enhanced and durable activity among all the catalysts examined. Both electronic and bifunctional effects may account for this enhancement based on the existing guideline for bimetallic catalysts.