PtAg Nanoparticle Electrocatalysts for the Glycerol Oxidation Reaction in Alkaline Medium

Binh Thi Xuan Lam,Masanobu Chiku,Hiroshi Inoue,Eiji Higuchi

doi:10.4236/anp.2016.53018

Abstract

To improve the activity for glycerol oxidation reaction (GOR) of Pt, PtAg (mole ratio of Pt/Ag = 3 and 1) alloy nanoparticle-loaded carbon black (Pt/CB, PtAg(3:1)/CB, PtAg(1:1)/CB) catalysts were prepared by a wet method. The resultant catalysts, moreover, were heat-treated in a N2 atmosphere at 200°C. The alloying of Pt with Ag for each PtAg/CB was confirmed by X-ray diffractometry and electron dispersive X-ray spectrometry. The heat-treatment did not change the crystal structure of the PtAg alloys and increased their particle size. X-ray photoelectron spectroscopy exhibited that stabilizers were completely removed from the PtAg alloy surface, and the Pt4f and Ag3d doublets due to metallic Pt and Ag, respectively, shifted to lower binding energies, supporting the alloying of Pt with Ag. Both PtAg/CB electrodes had two oxidation waves of glycerol irrespective of heat-treatment, which was different from the Pt/CB electrode. The onset potential of the first oxidation wave was -0.60 V, which was 0.20 V less positive than that for the Pt/CB electrode, indicating the alloying of Pt with Ag greatly improved the GOR activity of Pt. The heat-treated PtAg(3:1)/ CB electrode improved the GOR current density of the second oxidation peak. In the potentiostatic electrolysis at -0.1 and 0 V for both PtAg/CB electrodes, the ratio of oxidation current density at 60 min to that at 5 min (j60/j5), an indicator of the catalyst deterioration, at 0 V was higher than that at -0.1 V, because the adsorbed oxidation intermediates were greatly consumed at the larger overpotential. The heat-treatment of the PtAg(3:1)/CB electrode increased the j60/j5 value at -0.1 V but decreased that at 0 V. This could be attributed to the formation of high-order oxidation intermediates which might have stronger poisoning effect.

Highlights

Biodiesel fuel (BDF) is known as a carbon-neutral fuel which is produced with glycerol byproduct through the transesterification of vegetable fats and oils or long-chain alkyl esters with methanol
We developed the Pd-Ag and Pd-Au alloy nanoparticle catalysts by a wet method at room temperature, and found that the alloying of Pd with Ag was effective for making the onset potential of the glycerol oxidation reaction (GOR) current (Eonset) lower, whereas the alloying with Au made the maximum GOR current higher [8]
PtAg alloys have been used for various alcohol oxidation reactions in alkaline media, but as for GOR only one paper has been published [11], and described that Pt was deposited on Ag nanowires by the partial galvanic displacement, and the alloying of Pt with Ag occurred during the Pt deposition to form the PtAg nanoparticles which were superior in GOR activity and durability to Pt black [11]

Summary

Introduction

Biodiesel fuel (BDF) is known as a carbon-neutral fuel which is produced with glycerol byproduct through the transesterification of vegetable fats and oils or long-chain alkyl esters with methanol. PtAg alloys have been used for various alcohol oxidation reactions in alkaline media, but as for GOR only one paper has been published [11], and described that Pt was deposited on Ag nanowires by the partial galvanic displacement, and the alloying of Pt with Ag occurred during the Pt deposition to form the PtAg nanoparticles which were superior in GOR activity and durability to Pt black [11].

Results

Conclusion