Abstract Pt3Co nanoparticles are promising catalyst candidates for fuel-cell applications because their catalytic performances are superior to pure Pt nanoparticles. Fundamental insights into the thermostability of Pt3Co nanoparticles are critical for their syntheses, post-treatments, and ultimate applications. In this article, the thermal stability of Pt3Co nanoparticles has been investigated by molecular dynamics simulations. Two types of structures, chemically disordered alloy and ordered intermetallic compound, are considered. Besides, two-atomic-layered Pt and Co have been introduced to coat the Pt3Co nanoparticles to form Pt3Co-Pt and Pt3Co-Co core-shell nanoparticles. The simulated results reveal that the ordered intermetallic Pt3Co nanoparticles exhibit better thermal stability than the disordered alloy ones. Pt coating is greatly superior to Co coating for improving both structural and thermal stability of Pt3Co nanoparticles. For Pt3Co and Pt coated Pt3Co nanoparticles, the overall melting simultaneously happens in both Pt and Co. However, Co-coated surface induces the two-stage melting of Pt3Co nanoparticles at large sizes; it markedly decreases the thermal stability of the nanoparticles at small sizes, resulting in the melting point even lower than pure Co ones. The remarkably lowered melting temperature is associated with the order-to-disorder transformation in the Co-coated shell and the appreciable change of particle shape before surface premelting.

中文翻译：

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Pt3Co 纳米粒子热稳定性的原子尺度洞察：无序合金与有序金属间化合物的比较

摘要 Pt3Co 纳米粒子由于其催化性能优于纯 Pt 纳米粒子，是燃料电池应用的有前途的催化剂候选者。对 Pt3Co 纳米颗粒的热稳定性的基本了解对其合成、后处理和最终应用至关重要。在本文中，通过分子动力学模拟研究了 Pt3Co 纳米颗粒的热稳定性。考虑了两种类型的结构，化学无序合金和有序金属间化合物。此外，还引入了双原子层状 Pt 和 Co 来涂覆 Pt3Co 纳米颗粒，形成 Pt3Co-Pt 和 Pt3Co-Co 核壳纳米颗粒。模拟结果表明，有序金属间 Pt3Co 纳米粒子比无序合金纳米粒子表现出更好的热稳定性。Pt 涂层在改善 Pt3Co 纳米粒子的结构和热稳定性方面大大优于 Co 涂层。对于 Pt3Co 和 Pt 包覆的 Pt3Co 纳米粒子，整体熔化同时发生在 Pt 和 Co 中。然而，Co 包覆的表面诱导了大尺寸 Pt3Co 纳米粒子的两阶段熔化；它显着降低了小尺寸纳米粒子的热稳定性，导致熔点甚至低于纯 Co 的熔点。显着降低的熔化温度与 Co 包覆壳中的有序到无序转变以及表面预熔前颗粒形状的明显变化有关。然而，Co 包覆的表面会诱导大尺寸 Pt3Co 纳米颗粒的两阶段熔化；它显着降低了小尺寸纳米粒子的热稳定性，导致熔点甚至低于纯 Co 的熔点。显着降低的熔化温度与 Co 包覆壳中的有序到无序转变以及表面预熔前颗粒形状的明显变化有关。然而，Co 包覆的表面会诱导大尺寸 Pt3Co 纳米颗粒的两阶段熔化；它显着降低了小尺寸纳米粒子的热稳定性，导致熔点甚至低于纯 Co 的熔点。显着降低的熔化温度与 Co 包覆壳中的有序到无序转变以及表面预熔前颗粒形状的明显变化有关。