Pt: Ni 原子比对Pt-Ni八面体氧还原活性的影响研究

Influence of the Pt:Ni atomic ratio on the oxygen reduction reaction activities of Pt-Ni octahedral nanoparticles

摘要:

由(111)面包围的八面体Pt-Ni纳米颗粒被认为是有前途的氧还原反应(ORR)催化剂。据报道,Pt Ni八面体纳米粒子的ORR活性受Pt∶Ni原子比的影响很大。Pt-Ni八面体的Pt:Ni原子比与相应的ORR活性之间的关系为火山曲线并且缺乏相应解释。本文通过合成Pt3Ni、PtNi和PtNi2三种原子比的Pt-Ni八面体纳米粒子,发现Pt3Ni＞PtNi2> PtNi的ORR面积比活性差异。同时,在相同的Pt负载下,ORR质量比活性的顺序为Pt3Ni≈PtNi2> PtNi。表面晶格收缩和Pt的利用率被认为是解释这些现象的原因。表面晶格收缩的程度Pt3Ni＞PtNi2> PtNi,这与ORR面积比活性的顺序一致,这挑战了以前的经验,即Ni越多地结合到Pt晶格中,表面晶格收缩就越高。而质量比活性是面积比活性与表面铂利用之间的平衡。结果表明,通过调节表面张力和表面铂的利用可以调节ORR活性。

Abstract:

Octahedral Pt-Ni nanoparticles surrounded by (111) facet are considered as promising oxygen reduction reaction (ORR) catalysts. It has been reported that the ORR activities of Pt-Ni octahedral nanoparticles are greatly influenced by the Pt:Ni atomic ratio. The relationship between the Pt:Ni atomic ratio of Pt-Ni octahedron and the corresponding ORR activity is presented as a volcano plot without explanation. Herein, by synthesizing Pt-Ni octahedral nanoparticles with composition of Pt₃Ni, PtNi and PtNi₂, we found an abnormal ORR specific activities in the order of Pt₃Ni> PtNi₂> PtNi. Meanwhile, with the same Pt loading, the sequence of ORR mass activity is Pt₃Ni≈ PtNi₂> PtNi. The surface lattice contraction and the utilization of Pt were considered to explain these phenomenon. The extent of surface lattice contraction is decreased as Pt₃Ni> PtNi₂> PtNi, consistent with the sequence of ORR specific activity, which challenges the previous experience that the more Ni was incorporated into the Pt lattice, the higher the surface lattice contraction yielded. While the mass activity is a balance between specific activity and surface Pt utilization. The results indicated that the ORR activity can be adjusted by tuning the surface tension and surface Pt utilization.