Characterization of Carbon-Supported AuPt Nanoparticles for Electrocatalytic Methanol Oxidation Reaction

Abstract

In view of the recent finding that the bimetallic AuPt nanoparticles prepared by molecular-capping-based colloidal synthesis and subsequent assembly on carbon black support and thermal activation treatment exhibit alloy properties, which is in sharp contrast to the bimetallic miscibility gap known for the bulk counterparts in a wide composition range, there is a clear need to assess the electrocatalytic properties of the catalysts prepared with different bimetallic composition and different thermal treatment temperatures. This paper reports recent results of such an investigation of the electrocatalytic methanol oxidation reaction (MOR) activities of the carbon-supported AuPt nanoparticle catalysts with different bimetallic composition and thermal treatment temperatures. Au m Pt 100-m nanoparticles of 2-3 nm core sizes with different atomic compositions ranging from 10% to 90% Au (m ) 10∼90) have been synthesized by controlling the feeding of the metal precursors used in the synthesis. The electrocatalytic MOR activities of the carbon-supported AuPt bimetallic catalysts were characterized in alkaline electrolytes. The catalysts with 65% to 85% Au and treated at 500 °C were found to exhibit maximum electrocatalytic activities in the alkaline electrolytes. The findings, together with a comparison with some well-documented catalysts as well as recent experimental and theoretical modeling results, have revealed important insights into the participation of CO ad and OH ad on Au sites in the catalytic reaction of Pt in the AuPt alloys with ∼75% Au. The insights are useful for understanding the correlation of the bifunctional electrocatalytic activity of the bimetallic nanoparticle catalysts with the bimetallic composition and the thermal treatment temperatures.

Bimetallic Au-Pt nanoparticles synthesized by radiolysis: Application in electro-catalysis

“…Table 1 gathers the main literature cyclic voltammetry characteristics for pure Au nanoparticles supported on carbon (Au/C), pure Pt/C, Au-Pt nanoparticles synthesized using various procedures and also those of the present work. Even though disparity in experimental conditions precludes quantitative comparisons, two trends emerge: i) the characteristics measured in the present work with 0.5 M MeOH in alkaline medium comply with literature values; 31,32 ii) the potential characteristics for the cyclic voltammograms, including the faradaic current onset potential (E onset ), the forward peak potential (E f ) and the backward peak potential (E b ) are smaller for AuPt than the corresponding values for pure Au or pure Pt. Analysis of the particle suspension gives: for Pt (1.91 ± 0.01) mg/mL and for Au (2.09 ± 0.01) mg/mL.…”

Au as an efficient promoter for electrocatalytic oxidation of formic acid and carbon monoxide: a comparison between Pt-on-Au and PtAu alloy catalysts

“…The facts show that a Pt-based catalyst has improved the catalytic performance of FA oxidation compared with pure Pt [14][15][16][17][18][19]. Among various Pt-based catalysts, bimetallic PtAu is one of the best catalysts for formic acid oxidation, which is attributed to its enhanced activity [11,20,21] and stability against dissolution by raising the Pt oxidation potential [20,[22][23][24][25][26]. Moreover, the incorporation of Au into Pt could lead to the segregation of Pt sites and further reduce the number of adsorption sites for CO, thereby yielding an improvement in the activity of FA oxidation [13,20,27].…”

Gold-platinum alloys and Vegard's law on the nanoscale

“…There appears to be a serious discrepancy between theory and experiment: Theoretical calculations find core-shell particles as the energetically lowest pattern, [18][19][20][21][22][23] whereas x-ray diffraction typically detects randomly mixed alloys. 13,[24][25][26][27] By calculating the structure and x-ray diffraction patterns of Au-Pt NPs we show here that shells of Au are poorly visible in the x-ray patterns and that Vegard's law is ambiguous on the nanoscale.…”