The formation of iron phosphide nanoparticles (Fe_xP 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, P₄(MesCO)₄. We demonstrate that this compound can be used as a stoichiometric source of P(0) species in order to synthesize FeP and Fe₂P 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_xP NPs is provided which relies on the use of a stoichiometric and single P‐source. We then explore the electrocatalytic properties of Fe_xP 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 Fe₂P. 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.

中文翻译：

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用于结晶和非晶态磷铁纳米催化剂的相选择合成的单分子化学计量P源

磷化铁纳米颗粒（Fe _x P NPs）的形成是一个经过充分研究的过程。它通常使用对空气敏感的磷前体，例如正辛基膦或白磷。在这项研究中，我们报告了一个非常稳定的四（酰基）环四膦，P ₄（MesCO）₄的合成和表征。我们证明该化合物可以用作P（0）物种的化学计量来源以合成FeP和Fe ₂P纳米颗粒仅在250°C时。该可调过程提供了一种使具有不同组成和结晶度的纳米颗粒单分散的途径。我们将X‐射线光电子能谱（XPS）和原子对分布函数（PDF）结合在一起，以研究非晶态和结晶态材料中的局部有序和键合。我们显示结晶FeP经由中间非晶相（在较低温度下获得）形成，该非晶相呈现与结晶样品相似的局部有序。从这项工作的结果，可以更好地了解非晶和结晶Fe _x P NP的形成机理，这取决于使用化学计量和单一P源。然后，我们探索Fe _x的电催化性能在酸性和中性电解质中用于氢释放反应（HER）的P纳米颗粒。在两种电解质中，非晶态FeP均比晶态FeP更有效，而晶态FeP本身比晶态Fe ₂ P更有效。我们的研究为电催化中非晶态金属磷化物相的系统研究铺平了道路。它还显示了PDF在表征此类纳米材料方面的有益特性，这极具挑战性。