Controlled synthesis of carbon-supported Co catalysts from single-sites to nanoparticles: characterization of the structural transformation and investigation of their oxidation catalysis
Controlled synthesis of carbon-supported Co catalysts from single-sites to nanoparticles: characterization of the structural transformation and investigation of their oxidation catalysis
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DOI：
10.1039/c6cp06388h
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发表时间：
2017-02-21
影响因子：
3.3
通讯作者：
Yamashita, Hiromi
中科院分区：
文献类型：
--
作者：
Nakatsuka, Kazuki;Yoshii, Takeharu;Yamashita, Hiromi
实现对固体表面催化活性中心的精确控制是功能化多相催化剂发展的重要目标之一。通过沉积Co（salen）络合物前驱体在热处理条件下的结构转变，可以成功地实现碳载Co催化剂从单活性中心到纳米颗粒的可控合成。使用XRD、原位XAFS和TEM等技术对所获得的结构进行表征。Co（salen）络合物的第一次分解是由Co-O-C键在约250 ℃下的解离引发的，这产生了孤立的单原子Co物质，同时甚至在高达400 ℃时仍保留Co-N-C键。当热处理温度超过450摄氏度时，Co-N-C键发生第二次分解以形成Co氧化物纳米团簇，随后在进一步增加热处理温度时生长Co NP。由于与碳载体的相互作用，单位点催化剂是高度分散的和电子缺陷的，并且与固有的Co（salen）络合物和纳米颗粒催化剂相比，显示出用于氧化H2O的活性和选择性。
Realizing accurate control of catalytically active centers on solid surfaces is one of the most essential goals in the development of functionalized heterogeneous catalysts. Controlled synthesis of carbon-supported Co catalysts from single-site to nanoparticles can be successfully achieved by the structural transformation of the deposited Co(salen) complex precursor under heat treatment. The obtained structures were characterized using techniques such as XRD, in situ XAFS, and TEM. The first decomposition of the Co(salen) complex is initiated by the dissociation of Co-O-C bonds at around 250 degrees C, which produces isolated single-atom Co species while retaining the Co-N-C bonds even up to 400 degrees C. When the heat treatment temperature exceeds 450 degrees C, the second decomposition of the Co-N-C bonds occurs to form Co oxide nanoclusters followed by the growth of Co NPs upon further increase of the heat treatment temperature. The single-site catalyst is highly dispersed and electronically deficient owing to the interaction with the carbon support, and shows activity and selectivity for the oxidation of ethylbenzene, as compared to the inherent Co(salen) complex and nanoparticle catalysts.