Au–Pt graded nano-alloy formation and its manifestation in small organics oxidation reaction

Abstract

A graded nano-alloy of Au 100Àx Pt x (x ¼ 7, 15, 23, 32, 40, 51, 62, 73 and 86) nanoparticles (NPs) formed by co-reduction of HAuCl 4 and H 2 PtCl 6 and the details are presented in this work. Au 100Àx Pt x NPs were characterized using surface plasmon resonance (SPR) absorption spectroscopy and transmission electron microscopy (TEM). The NPs were dispersed in Vulcan carbon (Au 100Àx Pt x /C) and annealed at 250, 400, 600 and 800 C. The as-formed and annealed materials were characterized using TEM, high resolution transmission electron microscopy (HR-TEM), powder X-ray diffraction (XRD), cyclic voltammetry (CV) and X-ray photoelectron spectroscopy (XPS). The CV studies indicate excess Pt on the surface, which is corroborated by XPS and HR-TEM results. The XRD data show that Vegard's law is obeyed by the asformed material and the materials annealed at 250 and 400 C, indicating that these materials are not nano-alloys. The studies clearly indicate that the formation of Au 100Àx Pt x NPs is kinetically controlled rather than being controlled by the thermodynamic stability. The results demonstrate the formation of graded alloys of Au 100Àx Pt x NPs. Pt excess in the graded nano-alloy is reflected favourably in the electrochemical oxidation of small organics. In the methanol oxidation reaction (MOR), the peak current value per mg of Pt increases as a function of x, reaches a maximum value at x ¼ 23 and the ratio of forward current to reverse current for MOR reached an unprecedented value of 6.7, which shows the catalyst's stability against poisoning by carbonaceous intermediates.

The structure-dependent enhancement of the oxygen reduction reaction performance of Co-based low Pt catalysts through Au addition

“…[33][34][35] The ECSAs of Au and Pt have been calculated from the charges corresponding to the reduction peaks for the Au and Pt surface oxides (A Au and A Pt ). The ratios of A Pt to (A Pt + A Au ), S Pt , used to describe the surface Pt and Au compositions 36 of the NPs are compared in Table S3 in ESI. For…”

Superior Electrocatalytic Performance of Au‐Pt Graded Nano‐Alloys Towards Alcohol Oxidation Reaction

“…The Synthesis and characterization of Au 100‐x Pt x /C materials were already reported by us . Briefly, the protocol involves co‐reduction of precursors to form Au 100‐x Pt x NPs in aqueous medium which was supported on Vulcan XC‐72 carbon.…”

“…The detailed description of synthesis and characterization of Au−Pt graded nano‐alloy NPs of different compositions have been previously published . Detailed analysis of Au−Pt NPs formation and its surface characteristics indicates the graded nano‐alloy formation and its annealing effects conclude the surface enrichment of Pt during synthesis and phase segregation occurs upon annealing the materials.…”

Nano-Porous Electro-Catalyst with Textured Surface Active Pd-Pt Islands for Efficient Methanol Tolerant Oxygen Reduction Reaction

“…Pd 100‐x Pt x /C materials. The spectra were de‐convoluted using Gaussian‐Lorentzian curve fitting with chi‐ square value less than 2. Figure S3(A) shows two set of peaks for Pd 3d 5/2 energy levels at around 335.10 eV & 340.48 eV and Pd 3d 3/2 energy levels at around 336.77 eV & 342.25 eV attributable to Pd(0) and Pd(II) in Pd 100‐x Mn 2x /C (x=15) alloy NPs.…”