Initial nucleation process in the synthesis of Platinum Nanoparticle from chloroplatinic acid
Initial nucleation process in the synthesis of Platinum Nanoparticle from chloroplatinic acid
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DOI：
10.1016/j.nantod.2021.101093
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发表时间：
2021-04
期刊：
影响因子：
17.4
通讯作者：
Qing Ye;Wei-Chun Xu;Shuangming Chen;Zhebin Wang;X. Duan;Hao Liu;Huan Zhang;Liang Sun;W. Yang;Chen Zhang;Jing Zhou
中科院分区：
文献类型：
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作者：
Qing Ye;Wei-Chun Xu;Shuangming Chen;Zhebin Wang;X. Duan;Hao Liu;Huan Zhang;Liang Sun;W. Yang;Chen Zhang;Jing Zhou
纳米材料的尺寸、形貌和多晶型是决定其物理化学性质的关键因素，而前驱体的成核过程对纳米材料的尺寸、形貌和多晶型有重要影响。理解原子尺度上的成核动力学是设计合成具有定制成分、形状和尺寸的纳米材料的基础。本文研究了在甲醇和甲醇/水混合体系中氯铂酸化学还原合成铂纳米粒子的成核过程。在协同作用与液相色谱质谱（LCMS）和第一性原理过渡态计算，在预成核阶段的具体反应过程中，前体氯铂酸（H2 PtCl 6）进行了两步还原过程，分别形成二价和非价Pt-包含集群，揭示。结果表明，在这两步反应中，水分子的存在通过质子传递机制降低了反应活化能，加快了反应速率。此外，通过自由能分析和从头算分子动力学模拟，我们确定了初始成核过程，其特征在于两个二价Pt（II）团簇之间形成Pt-Pt键。理论计算解释了预成核反应路径和成核过程，与LCMS测量和先前的XAFS结果一致。结果表明，氯铂酸/甲醇/水体系的成核过程比经典成核理论和前人的研究结果更为复杂。这一发现可能为贵金属纳米粒子的尺寸和形状控制合成提供了启示。
The size, morphology, and polymorphism of nano-materials, the key factors determining their physicochemical properties, are significantly affected by the nucleation processes from precursors. Understanding the nucleation kinetics at the atomic scale is fundamental to the designed synthesis of nano-materials with tailored composition, shape and size. Here we report our investigation on the nucleation process in synthesis Platinum nano-particles by chemical reduction of chloroplatinic acid in methanol and methanol/water mixed system. In synergy with the liquid chromatography mass spectrometry (LCMS) and first-principle transition-state calculations, specific reaction processes at the pre-nucleation stage are revealed in which the precursor chloroplatinic acid (H2PtCl6) undergoes a two-step reduction process to form divalent and non-valent Pt-contained clusters, respectively. It is found that in both steps, the presence of water molecular can lower the activation energy and accelerate the reaction rate through a proton transport mechanism. Moreover, through free energy analysis and ab-initio molecular dynamic simulation, we identified the initial nucleation process which is characterized by the formation of Pt-Pt bond between two divalent Pt (II)-contained clusters. The theoretical calculations explain the pre-nucleation reaction paths and the nucleation process, consistent with the LCMS measurements and previous XAFS results. This work indicates the nucleation processes in chloroplatinic acid/methanol/water system exhibit more complexities than that described by the classical nucleation theory as well as previous research results on the same system. The finding may shed light upon the size-and-shape-controlled synthesis of noble metal nanoparticles.