A Single Molecular Stoichiometric P‐Source for Phase‐Selective Synthesis of Crystalline and Amorphous Iron Phosphide Nanocatalysts

Abstract

The formation of iron phosphide nanoparticles (Fe x P NPs) is a well-studied process. It usually uses air-sensitive phosphorus precursors such as n-trioctylphosphine or white phosphorus. In this study, we report the synthesis and characterization of a remarkably stable tetrakis(acyl)cyclotetraphosphane, P 4 (MesCO) 4. We demonstrate that this compound can be used as a stoichiometric source of P(0) species in order to synthesize FeP and Fe 2 P nanoparticles at only 250 °C. This tunable process provides a route to monodisperse nanoparticles with different compositions and crystallinities. We combine X-Ray photoelectron spectroscopy (XPS) and atomic pair distribution function (PDF) in order to study the local order and bonding in the amorphous and crystalline materials. We show that crystalline FeP forms via an intermediate amorphous phase (obtained at a lower temperature) that presents local order similar to that of the crystalline sample. From the results of this work, a better understanding of the mechanism of the formation of amorphous and crystalline Fe x P NPs is provided which relies on the use of a stoichiometric and single P-source. We then explore the electrocatalytic properties of Fe x P nanoparticles for the hydrogen evolution reaction (HER) in acidic and neutral electrolytes. In both electrolytes, amorphous FeP is a more efficient catalyst than crystalline FeP, itself more efficient than crystalline Fe 2 P. Our study paves the way for a more systematic investigation of amorphous metal phosphide phases in electrocatalysis. It also shows the beneficial properties of PDF on the characterization of such nanomaterials, which is highly challenging.

Activity of Carbon-Encapsulated Ni12-Xfexp Catalysts for the Oxygen Evolution Reaction: Combination of High Activity and Stability

“…The values were in good agreement with the corresponding values reported for Ni 12 P 5 in the literature [71]. The P(V) and P(III) components have been interpreted as surface phosphate and phosphite [70], respectively. These may have formed as a result of the exposure of the nanoparticles to air while being stored at the ambient conditions.…”

“…For all the catalysts except Ni 10.8 Fe 1.2 P 5 , the P 2p region was deconvoluted into four peaks. For the Ni 12 P 5 catalyst, components at 129.4, 130.4, 132.6 and 133.3 eV, corresponding to phosphide, P(0), P (III) and P(V) species, respectively [69,70], proved to fit the spectra well. The values were in good agreement with the corresponding values reported for Ni 12 P 5 in the literature [71].…”

“…This indicates that two distinct Fe species are present in the samples. The Fe 2p 3∕2 peak can, in turn, be decomposed into two peaks approximately at 706 and 713 eV, respectively originating from the iron(0) and oxidized iron [68].…”

Heterostructured Cobalt Silicide Nanocrystals: Synthesis in Molten Salts, Ferromagnetism, and Electrocatalysis

“…Unlike bulk CoSi, the nanoparticles obtained in this work respond to a magnet, especially the core–shell nanoparticles. In order to eliminate the possible adventitious influence of ferromagnetic elemental Co clusters not detected by XRD or local TEM analysis, the total X-ray scattering pattern of the core–shell sample was analyzed by pair distribution function (PDF). − Fitting with only CoSi leads to a fairly acceptable (reliability factor R = 20.9%) but yet improvable solution. The addition of crystalline Si and amorphous silica (Table S2), in agreement with TEM analysis, yields the best refinement ( R = 15.6%, Figure ).…”

Compositional dependence of hydrodeoxygenation pathway selectivity for Ni2−xRhxP nanoparticle catalysts

“…Traditional synthesis methods for TMPs via impregnation of metal and phosphorus salts on high surface area metal-oxide supports followed by high temperature reduction can lead to broad particle size distributions, overreduction of metal salts to metal NPs, non-uniform phosphorus incorporation, and excess phosphate species that do not participate in TMP formation. 24,25 Solution synthesis routes, on the other hand, can enable control over composition, particle morphology, and crystal structure, 22,[26][27][28][29][30][31][32] providing model systems to understand the role of the second metal. Our group has previously established solution synthesis approaches to obtain Ni 2 P, Rh 2 P, and a variety of alloyed Ni 2 P NPs via the thermolysis of low-valent metal triphenylphosphine complexes.…”