Formation Process of Mesostructured PtRu Nanoparticles Electrodeposited on a Microemulsion Lyotropic Liquid Crystalline Template As Revealed by in Situ XRD, SAXS, and XANES

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• 作者：Yu-Chia Liang ; Yu-Wan Juan ; Kueih-Tzu Lu ; U-Ser Jeng ; Shin-An Chen ; Wei-Tsung Chuang ; Chun-Jen Su ; Chin-Lung Liu ; Chin-Wen Pao ; Jyh-Fu Lee ; Hwo-Shuenn Sheu ; Jin-Ming Chen
• 刊名：The Journal of Physical Chemistry C
• 出版年：2012
• 出版时间：December 20, 2012
• 年：2012
• 卷：116
• 期：50
• 页码：26649-26655
• 全文大小：487K
• 年卷期：v.116,no.50(December 20, 2012)
• ISSN：1932-7455

文摘

We investigated the formation process of mesostructured PtRu nanoparticles electrochemically reduced on a microemulsion lyotropic liquid-crystalline (MLLC) template. Nonionic surfactant decaethylene glycol monohexadecyl ether (Brij 56) and heptane (2 wt %) were used to form the MLLC template of a 2D hexagonal packing. The MLLC template was proved to be more stable than the corresponding LLC one without heptane, in the uptake of the metal precursors and the accommodation of the subsequently electroreduced PtRu nanoparticles. Structural evolution from the metallic ionic precursors to the mesomorphically ordered PtRu nanoparticles as directed by the MLLC template was traced using in situ small-angle X-ray scattering (SAXS), in situ X-ray diffraction (XRD), and X-ray absorption near-edge structure (XANES) spectra, further complementary by energy-dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), and field emission transmission electron microscopy (FE-TEM). Integrated results indicate an earlier and faster reduction of Pt precursors than that of Ru, upon electroreduction. Mixing aggregation of the subsequently reduced metallic atoms led to uniform PtRu nanoparticles, featuring in a Pt-rich alloy crystalline core and an amorphous Ru-rich shell. Confined by the MLLC template, growth of PtRu nanoparticles in the early stage saturated to a size of 4.5 nm. The subsequent growth was limited to the increase of number density of the nanoparticles. In the late stage, prolonged reduction led to highly populated nanoparticles that could further interconnect into an inverted mesostructure of the hexagonal packed MLLC template. The proposed MLLC template and the elucidated global and local structural evolution provide insights and implications on the growth mechanism and morphological control strategies for optimum syntheses of similarly mesostructured bimetallic nanoparticles of tailored size and degree of alloy.