Platinum–tin/carbon catalysts for ethanol oxidation: Influence of Sn content on the electroactivity and structural characteristics

Abstract

A series of Pt x -Sn y /C catalysts with different atomic ratios (x:y = 1:1, 2:1, 3:1) and diameters (~4 nm) were easily synthesized by a deposition process using formic acid as the reducing agent.Catalyst structure and chemical composition were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). XRD and SEM showed that the geometric environment was changed with Sn addition to the fcc Pt crystallites by forming a solid solution of Pt-Sn alloy phase for Pt 1 -Sn 1 /C catalyst, while for Pt 3 -Sn 1 /C and Pt 2 -Sn 1 /C, a decrease in Pt 4f binding energy was observed, and from the XPS results was attributed to charge transfer from Sn to Pt.From TEM results, it could be seen that Pt nanoparticles could be easily synthesized, even at a high metal load, without the use of expensive surfactants. The electrochemical behavior of catalysts during ethanol oxidation in acidic media was characterized and monitored in a half-cell test at room temperature by cyclic voltammetry, chronoamperometry, and anode potentiostatic polarization. The amount of Sn added affected the physical-chemical characteristics of the bimetallic catalysts; however, these catalysts did not show differences in the electrocatalytic activity towards ethanol oxidation. The presence or absence of alloy was a function of the Sn content on catalysts for the preparation method used. The behavior presented for Pt x -Sn y /C catalysts can be attributed to the so-called bifunctional mechanism, and to the electronic interaction between Pt and Sn.

Pt‐Sn Nanoparticles Supported on Carbon Nanodots as Anode Catalysts for Alcohol Electro‐oxidation in Acidic Conditions

“…It should be pointed that the O1s spectra for the Pt/CNDs electrocatalyst (Figure b) shows six peaks, the seventh peak observed for this Pt‐Sn/CNDs electrocatalyst was due to the presence of tin bonded through the oxygen atoms. When comparing the Pt/CNDs and Pt‐Sn/CNDs electrocatalysts, it is noted that the binding energies of the O1s spectrum for the Pt‐Sn/CNDs electrocatalyst shift to lower values to the due to the contribution of Sn which is believed to be bonded to the carbon nanodots through C=O functional group to form Sn‐O species . The deconvoluted C1s spectrum (Figure c) for the Pt‐Sn/CNDs electrocatalyst shows six peaks at 286.15 eV, 284.00 eV, 283.08 eV, 282.54 eV, 282.01 eV and 281.40 eV which were ascribed to the presence of O=C−C, C−C, Pt, C=C and Sn as labelled in the spectrum.…”

“…The improved activity of the Pt‐Sn/C electrocatalysts for ethanol oxidation is brought by Sn atoms which serve two functions; (i) Sn provides surface oxygen‐containing species which react with the CO‐like intermediates produced during the oxidation of ethanol and also (ii) modifies the platinum geometric structure resulting in improved activity. It has been observed that Pt‐Sn electrocatalysts give low onset potentials and high current densities during ethanol oxidation in acidic conditions .…”

“…The method for preparing the electrocatalyst also plays a vital role in determining the size and reactivity of the nanoparticles, hence the electroactivity. The Pt‐Sn nanoparticles have been synthesized by the Bönneman method , electrodeposition , borohydride reduction method , deposition method , formic acid method and the alcohol reduction method . The alcohol reduction method is the most commonly adopted procedure because of its simplicity.…”

Characterization of selectively etched halloysite nanotubes by acid treatment

“…In particular, the petroleum industry is leading the introduction of nanoparticles as supports for catalysts in several reactions. It has been reported the potential of activated carbon and carbon nanotubes (CNTs) as support for ethanol oxidation [4], aluminosilicates, cordierites [5], zeolites [6], other feldspars, kaolinite derivate such sespiolites [7], HNTs, etc., which allow the conversion of crude oil in a wide range of products.…”

Platinum-Based Carbon Nanodots Nanocatalysts for Direct Alcohol Fuel Cells

“…The Pt-Sn/C electrocatalyst yielded current values higher than those of Pt-Ru/C for both ethanol and methanol oxidation. The superior activity of the Pt-Sn/C nanocatalyst is brought by the "bifunctional" mechanism where Sn provides oxygen-containing species to react with the CO poisoning intermediates on the platinum sites [74][75][76][77][78].…”