Carbon-Supported IrNi Core–Shell Nanoparticles: Synthesis, Characterization, and Catalytic Activity
Carbon-Supported IrNi Core–Shell Nanoparticles: Synthesis, Characterization, and Catalytic Activity
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DOI：
10.1021/jp200746j
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发表时间：
2011-03
影响因子：
3.7
通讯作者：
K. Sasaki;Kurian A. Kuttiyiel;L. Barrio;D. Su;A. Frenkel;N. Marinkovic;D. Mahajan;R. Adzic
中科院分区：
文献类型：
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作者：
K. Sasaki;Kurian A. Kuttiyiel;L. Barrio;D. Su;A. Frenkel;N. Marinkovic;D. Mahajan;R. Adzic
我们通过化学还原和随后在H2中的热退火合成了碳支撑的IrNi核壳纳米颗粒，并通过各种实验方法验证了Ir壳在IrNi固溶体合金核上的形成。EXAFS分析与IrNi纳米颗粒由双层Ir壳和IrNi合金核组成的模型一致。原位XAS表明，Ir壳完全保护Ni原子的核心从氧化或溶解在酸性电解质在升高的电位。Ir壳层的形成在退火过程中，由于热偏析监测时间分辨同步辐射XRD测量，再加上Rietveld细化分析。发现IrNi纳米颗粒的H2氧化活性高于商业Pt/C催化剂。这主要是由于镍核诱导的Ir壳收缩，使表面的反应性较低的IrOH形成，和所得的更多的金属Ir表面变得更活跃的H2氧化。
We synthesized carbon-supported IrNi core–shell nanoparticles by chemical reduction and subsequent thermal annealing in H2, and verified the formation of Ir shells on IrNi solid solution alloy cores by various experimental methods. The EXAFS analysis is consistent with the model wherein the IrNi nanoparticles are composed of two-layer Ir shells and IrNi alloy cores. In situ XAS revealed that the Ir shells completely protect Ni atoms in the cores from oxidation or dissolution in an acid electrolyte under elevated potentials. The formation of Ir shell during annealing due to thermal segregation is monitored by time-resolved synchrotron XRD measurements, coupled with Rietveld refinement analyses. The H2 oxidation activity of the IrNi nanoparticles was found to be higher than that of a commercial Pt/C catalyst. This is predominantly due to Ni-core-induced Ir shell contraction that makes the surface less reactive for IrOH formation, and the resulting more metallic Ir surface becomes more active for H2 oxidatio...