Effect of AuM (M: Ag, Pt & Pd) bimetallic nanoparticles on the sorbitol electro-oxidation in alkaline medium

Abstract In this work, the effect of the second metal of AuM (M: Ag, Pd & Pt) materials on the sorbitol electro-oxidation reaction (SOR) in alkaline medium was evaluated. For this purpose, AuM nanoparticles were synthesized following the Brust’s method. The obtained nanoparticles presented similar average particle size (~7 nm), while the gold content ranged between 53 and 77 atomic %, the Vulcan carbon support loading was found to be close to 80 ± 5 wt%. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electrochemical analyses confirmed the formation of the bimetallic catalysts and revealed close electronic interactions between the noble metals. Cyclic voltammograms performed using 0.1 M sorbitol in 0.3 M KOH indicated that AuPt/C displayed the lowest onset potential (−0.36 V vs. NHE), which is 120 mV lower to that determined for Au/C as the reference material. Furthermore, AuPd/C catalyst presented the highest current density (43.65 [mA mgAuPd−1] at a fixed potential of 0.14 V vs. NHE). Further experiments varying the sorbitol and KOH concentrations, the scan rate and the operating temperature were performed as well as electrochemical impedance spectroscopy (EIS) experiments. These results shown that the SOR followed the typical trend for the electro-oxidation of polyol fuels (such as glycerol), where Pt promotes lower onset potentials, but the adsorption of intermediates limits the maximum current density in comparison with Pd-based catalysts. As summary, this study found that AuPd and Pd-containing materials could be excellent candidates for sorbitol oxidation in alkaline medium.