Structure of Pt_nNi Nanoparticles Electrocatalysts Investigated by X-ray Absorption Spectroscopy

Abstract

Carbon supported Pt−Ni nanoparticles (NPs) electrocatalysts with nominal Pt/Ni atomic ratios of 3:1, 2:1, and 1:1, denoted as Pt 3 Ni/C, Pt 2 Ni/C, and Pt 1 Ni/C, respectively, were obtained by a modified polyol process. The structure of Pt n Ni/C (n = 3, 2, 1) electrocatalysts was studied by using an X-ray absorption spectroscopy technique combined with X-ray diffraction and transmission electron microscopy. Significantly, the NPs of Pt 3 Ni/C in air are demonstrated to have a quasi core−shell structure consisting of a core of metallic Pt surrounded by many small NiO x clusters. In contrast, both Pt 2 Ni/C and Pt 1 Ni/C are demonstrated to have an alloy structure with partial oxidation on the surface. Under the atmosphere of H 2 at 393 K, the Pt n Ni/C became the expected bimetallic alloy. At last, we discuss the effect of Ni amount on the structure of Pt n Ni/C and estimate their possible catalytic activity for methanol oxidation reaction. Our results further confirmed that the structure of Pt−Ni NPs can be influenced by Ni amount and this effect may be enlarged by environment effects.

High‐Performance Bismuth‐Doped Nickel Aerogel Electrocatalyst for the Methanol Oxidation Reaction

“…In general, the shapes of the Ni K-edge for the Ni 97 Bi 3 and Ni 55 Bi 45 aerogels are similar to the Ni foil, and the whiteline intensity at approximately 8351 eV is much weaker than the reported NiO. [14] These results,i nc ombination with the XPS results,indicate that the Ni in the Ni 97 Bi 3 and Ni 55 Bi 45 aerogels is statistically metallic,but on the surface it is mainly in an oxidized state.…”

Surface Segregation in Bimetallic Nanoparticles: A Critical Issue in Electrocatalyst Engineering

“…Nevertheless, due to the weak bonding with H and C, Ni surface segregation is not remarkable in a reducing atmosphere (such as H 2 or CO) . This was also confirmed by experiments . For example, Rentao et al reported reversible structural changes of Pt–Ni NPs (5∼20 nm) in alternating H 2 and O 2 environments .…”

A DFT Study on the O2 Adsorption Properties of Supported PtNi Clusters

“…Further experimental work has focused on the preparation of small PtNi nanoparticles (NPs) ≤ 5 nm, with varying Pt-loading. These NPs have well-controlled octahedral geometries (FCC-type atomic arrangements) displaying extensive (111) facets, aiming for similar catalytic properties as the extended surface [12][13][14][15][16][17][18][19][20][21]. Thus, the maximisation of large surface areas offered by bimetallic NPs makes them ideal as catalysts for novel fuel cell applications.…”