Combined small- and wide-angle X-ray scattering studies on oxide-supported Pt nanoparticles prepared by a CVS and CVD process
Combined small- and wide-angle X-ray scattering studies on oxide-supported Pt nanoparticles prepared by a CVS and CVD process
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对 CVS 和 CVD 工艺制备的氧化物负载 Pt 纳米颗粒进行小角和广角 X 射线散射联合研究
DOI：
10.1016/j.powtec.2014.11.028
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发表时间：
2015
影响因子：
5.2
通讯作者：
Hermann Nirschl
中科院分区：
文献类型：
--
作者：
Xiaoai Guo;Kun Gao;Alexander Gutsche;Martin Seipenbusch;Hermann Nirschl
利用自行研制的小角X射线散射（SAXS）和广角X射线散射（WAXS）实验系统，对常压下CVS/CVD法制备的各种模型氧化物负载金属催化剂颗粒（SiO2、TiO 2和Al 2 O3负载Pt纳米点）进行了研究。它已被证明，同时SAXS和WAXS分析提供了一个结构的洞察到负载型金属催化剂的复杂性，允许定量研究的形态特征的合成氧化物负载型催化剂颗粒和精细结构，包括初级颗粒，内部亚基，质量分形维数的聚集体，表面粗糙度，和微晶特性以及Pt纳米点。所研究的氧化物载体颗粒覆盖55-150 nm的尺寸范围，Pt纳米点的尺寸范围为1.8-15.8 nm。将SAXS和WAXS的结果与TEM和XRD参考数据库的结果进行了比较，发现两者具有很好的一致性。实验结果表明，SAXS比WAXS更有效地确定Pt点的尺寸，特别是对于小于2的Pt点，4 nm，这是由于在宽角度处散射信号的重叠效应以及由此导致的难以辨别小Pt的宽WAXS峰从支持的背景点。在合成过程中，通过将一定量的氧化铝混合到其他氧化物载体颗粒中，观察到载体颗粒表面的形态学改性，通过使用SAXS定量测定描述表面粗糙度的表面分形维数。同时定量表征载体颗粒结构和金属催化剂纳米颗粒有助于更好地理解合成条件如何影响所得载体颗粒的结构，以及这反过来如何影响催化剂性能，如金属纳米颗粒在载体上的团聚或烧结，以进一步优化合成工艺并制备更好的负载型金属催化剂纳米颗粒。
Various model oxide-supported metal catalyst particles (Pt nanodots supported on silica, titania and alumina) prepared by a CVS/CVD process at atmospheric pressure have been studied by using a self-developed SAXS and WAXS laboratory system. It has been shown that simultaneous SAXS and WAXS analyses offer a structural insight into the complexity of the supported metal catalysts, allowing quantitative study on the morphological characteristics of the synthesized oxide-supported catalyst particles and fine structures, including primary particles, internal subunits, mass fractal dimension of the aggregates, surface roughness, and crystallite properties as well as the Pt nanodots. The oxide support particles under study cover a size range of 55–150 nm and the Pt nanodots are in the size range of 1.8–15.8 nm. The SAXS and WAXS results were compared with those by TEM and the XRD reference database, and a good agreement has been found. Experimental findings indicated that SAXS appears to be more effective than WAXS for determining the Pt dot size, especially for Pt dots smaller than 2–4 nm due to the overlapping effect of the scattering signals at wide angles and the resultant difficulty in discerning the broad WAXS peaks of small Pt dots from the support background. The morphological modification of the support particle surface by mixing a certain amount of alumina into the other oxide support particles during the synthesis process has been observed through quantitative determination of the surface fractal dimension describing the surface roughness using SAXS. Simultaneous quantitative characterization of support particle structures and metal catalyst nanoparticles helped to better understand how synthesis conditions influence the resulting structures of the support particles and how this in turn affects the catalyst properties like the agglomeration or sintering of metal nanoparticles on the supports, to further optimize the synthesis process and prepare better supported metal catalyst nanoparticles.
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