Monitoring the formation of PtNi nanoalloys supported on hollow graphitic spheres usingin situpair distribution function analysis

Abstract

This article aims to address the formation and the structural disordering/ordering phenomena of PtNi nanoalloys supported on hollow graphitic spheres (HGSs) using pair distribution function (PDF) analysis under ex situ/in situ data collection conditions. Starting from small nanoparticles (10-15 Å in diameter) embedded in HGSs, structural changes were monitored during stepwise heating and cooling of the sample using in situ PDF analysis. In order to evaluate the conventional synthesis route for the production of PtNi nanoalloys supported on HGSs, ex situ PDF experiments were performed before and after heat treatment in a furnace. The studies demonstrate that the local structure of the in situ synthesised PtNi nanoalloy differs from its ex situ synthesised counterpart. A partially ordered PtNi nanoalloy was obtained during the stepwise in situ cooling of the precursor, whereas the conventional ex situ synthesis route did not lead to the formation of an ordered crystal structure. In this study we could show that rapid heating and cooling results in a disordered PtNi alloy whereas slow heating and cooling leads to disorder-order transitions in PtNi.

Bridging Structural Inhomogeneity to Functionality: Pair Distribution Function Methods for Functional Materials Development

“…Furthermore, the structural changes of PtNi nanoalloys supported on hollow graphitic spheres (HGSs) were probed during the synthesis route, in order to reveal the structural order/disorder phenomena. [ 270 ] The results show that a disordered PtNi alloy could be formed upon rapid heating, whereas a disorder–order transition occurs under slow heating‐cooling procedure (Figure 12c).…”

Pt-Based Intermetallic Nanocrystals in Cathode Catalysts for Proton Exchange Membrane Fuel Cells: From Precise Synthesis to Oxygen Reduction Reaction Strategy

“…Similar results are confirmed for the Pt-Ni system. Weidenthaler et al analyzed the formation mechanism of the ordered-disordered transformation of Pt-Ni alloys during stepwise heat treatment using in situ high-resolution X-ray powder diffraction (HR-XRPD) and X-ray paired distribution (PDF) analyses [62]. The comparative characterization of in-situ and ex-situ methods demonstrates that in the Pt-Ni-ordered reconfiguration process, a slow stepwise cooling process leads to the generation of partially ordered structures (Figure 3a).…”

“…In the extended X-ray absorption fine structure (EXAFS) analysis, the intermetallic nanocrystals have more Pt-M bonds and less Pt-Pt, M-M bonds than disordered alloys, due to a higher alloying degree [14]. The Rietveld analysis and PDF analysis are also used to determine whether an ordered structure has been generated by comparing the fit residual [62]. New properties due to the ordered structure can also be used to discern whether the superstructure is generated or not.…”

Sodium-Ion Battery Anode Construction with SnP x Crystal Domain in Amorphous Phosphorus Matrix

“…Therefore, it is required to develop new technologies for the structural investigation and quantification. The pair distribution function (PDF) is a powerful characterization technique, which can not only provide local structure information for complicated systems but also quantify the components in ordered or even disordered materials [29][30][31][32][33]. However, owing to the light weight of P, PDF has rarely been used in P-/Sn-based anode materials, making the further structural transformation and reaction mechanism indistinct [13,34].…”