Structural Study of Pt–Fe Nanoparticles: New Insights into Pt Bimetallic Nanoparticle Formation with Oxidized Fe Species

Abstract

A combination of physicochemical methods allowed us to assess a structure of comparatively monodisperse 3–4 nm Pt–Fe x O y nanoparticles (NPs) synthesized by thermal decomposition of platinum acetylacetonate in the presence of iron oxide NPs as an iron source. Unlike traditional PtFe alloys composed of zerovalent Pt and Fe species with the surface enriched by Pt atoms, the NPs discussed in this work contain Pt(0) and oxidized Fe species (most probably Fe3+ or Fe2+) as is proven by X-ray photoelectron spectroscopy (XPS). Angular dependence XPS measurements demonstrated the absence of the core–shell structure, although a minor enrichment of the NP surface with Fe species was observed. High-resolution transmission electron microscopy and X-ray powder diffraction (XRD) reveal that these Pt–Fe x O y NPs are not alloys, but consist of different domains; i.e., they have a “cluster-in-cluster” morphology. A comparison of the XPS and XRD data allowed us to conclude that the NPs also include amorphous iron oxide. These results allow better understanding of the mechanism of such NP formation and possible predictions of their catalytic performance.

General Synthetic Strategy for Libraries of Supported Multicomponent Metal Nanoparticles

“…Pt 4f 7/2 and Pt 4f 5/2 bands were observed at 72.0 and 75.3 eV, which are in agreement with values reported for platinum metal in binary and ternary alloy systems. ,,, The Ni 2p 3/2 and Ni 2p 1/2 peaks were observed at 853.1 and 870.4 eV, and Fe 2p 3/2 and Fe 2p 1/2 peaks were observed at 707.6 and 720.7 eV, together with a Ni Auger feature at 712.1 eV. These results are in accord with XPS data reported for zero-valent nickel and iron. ,,, The Pt/Ni/Fe ratio in PtNiFe@NPCC (2.5 wt % Pt, 3.81 wt % Ni, and 1.6 wt % Fe) is 1:5.2:2.3, as determined by ICP-AES (Table ). This is consistent with the ratio of Pt/Ni/Fe = 1:5.14:2.31 in the ZIF-8/Pt@NiFe-TA precursor (Table S1).…”

“…These results are in accord with XPS data reported for zero-valent nickel and iron. 8,10,29,30 The Pt/Ni/Fe ratio in PtNiFe@NPCC (2.5 wt % Pt, 3.81 wt % Ni, and 1.6 wt % Fe) is 1:5.2:2.3, as determined by ICP-AES (Table 1). This is consistent with the ratio of Pt/Ni/Fe = 1:5.14:2.31 in the ZIF-8/Pt@NiFe-TA precursor (Table S1).…”

Design of ruthenium/iron oxide nanoparticle mixtures for hydrogenation of nitrobenzene

“…In our preceding paper, it was determined that for the 11 nm oxidized iron oxide NPs, the atomic ratio of Fe 2+ /Fe 3+ is 0.18, which matches 54 mol.% of the Fe 3 O 4 phase. 36 In general, the values of Fe 2p binding energies (BE) ranging from 710.7 eV to 711.2 eV without satellite structure indicate stoichiometric Fe 3 O 4 species. 37,38 Smaller iron oxide NPs (8.1 nm) in this study exhibit a weak satellite at 718.9 eV BE in the Fe 3p 3/2 region characteristic of Fe 3+ ions (Fig.…”

Recent advances in noble metal based composite nanocatalysts: colloidal synthesis, properties, and catalytic applications

“…4). 88 Pan et al synthesized carbon supported Pd-Fe composite nanoparticles with a small particle size and the single-phase fcc disordered structure using the precursors of Pd(CH 3 COO) 2 and Fe(CH 3 COO) 2 in the absence of additional stabilizers, giving an excellent electrocatalytic activity for the oxygen reduction reactions (ORR). 84 This method has been extended to use other precursors including PdCl 2 86,89 and [Pd(NH 3 ) 4 ](NO 3 ) 2 85,90 In addition, the thermal decomposition method has also been used to synthesize Au-based 89 and Ag-based 91 composite nanoparticles.…”