Crystal structure and morphology control of CoO and $Pd/C_{60}$ nanoparticles = 코발트 산화물 및 팔라듐/풀러렌 나노입자의 결정구조와 형상조절에 관한 연구

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This study involves the synthesis and characterization of hexagonal, cubic CoO nanoparticles and $Pd/C_{60}$ hybrid nanoparticles for fuel cell catalyst. First, we report a simple, reliable synthesis of size-controlled CoO nanoparticles with different phases, hexagonal and cubic structures from thermal decomposition of a single precursor $Co(acac)_3$ (acac = acetylacetonate) in oleylamine. CoO nanoparticles with different structures were prepared by controlling the reaction time and temperature during the nucleation and growth of nanocrystals. A slurry of $Co(acac)_3$ in oleylamine (1:200 molar ratio) was heated at $135\deg C$ for ca. 5 min under an atmosphere of argon to make clear green solution, which was further heated at $200\deg C$ for 1 h. The resulting reaction mixture was cooled to room temperature to form a green suspension. The low resolution transmission electron microscope (TEM) image of the green product shows rod shaped nanocrystals. Selected area electron diffraction pattern (SAED) of the nanocrystals is consistent with hexagonal ZnO ($\It{P63mc}$, a = 3.25, and c = 5.207). Large CoO nanocrystals were obtained at a higher concentration of precursor. As the sizes of nanocrystals became larger, rod shape of them changed to hexagonal pyramid shape. Pure cubic CoO ($\It{Fm3m}$, a = 4.26) was obtained by lengthening the reaction time at a low temperature of $135\deg C$ until 5h. Long reaction at $135\deg C$ presumably gave a favorable condition for cubic CoO seeds growth informing that cubic CoO is thermodynamic product, and hexagonal CoO is kinetic product. A simple change in the concentration of precursor and the reaction temperature resulted in variation of the cubic CoO nanocrystal size. Second, hexagonal and cubic CoO nanoparticles were prepared by using another precursor $Co(acac)_2$ in oleylamine. In these syntheses, addition of water was used as only controlling factor of crystal structure. The decomposition products were hexagonal...
Park, Joon-Taikresearcher박준택researcher
한국과학기술원 : 화학과,
Issue Date
418740/325007  / 020037356

한국과학기술원 : 화학과, 한국과학기술원 : 화학과, 2010.2, [ vii, 67p ]


나노입자; 연료전지; 팔라듐; 결정구조; 코발트 산화물; nanoparticle; fuel cell; palladium; cobalt oxide; crystal structure

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