Controlled Synthesis Of CoO Nanocrystals And Their Magnetic And Electrocatalytic Properties

Cobalt oxides nanocrystals have extensive application prospects in the field of optics,magnetic materials,catalysis and biomedicine because of their special physical and chemical properties.As a kind of nanoscale cobalt oxides,the cobalt(?)oxide(CoO)nanocrystals have more wide applications in batteries,electronics,catalytic and so on.Since the performances of CoO nanocrystals are dependent greatly on their shapes and structures,the controllable synthesis of CoO nanocrystals with desired shape and crystal phases has received intensive interest.In this thesis,we synthesized CoO nanocrystals with different crystal structures and morphology by organic solution method.By studying the influences of different preparation parameters to the final crystalline structure and morphology,we prepared cubic CoO(c-CoO)and wurtzite CoO(h-CoO)nanorods.Furthermore,we have made the preliminary discussion about their formation mechanisms,magnetic properties and electric catalytic performance.The main conclusions are summed up as follows:(1)By using cobalt stearate as precursor,1-octadecene as solvent,the water as a controlling parameter,we synthesized two kinds of CoO nanocrystals.For the experimental system without water,we synthesized the CoO multi-branches nanorods along the[100]direction with a cubic crystalline structure.For the experimental system with water,we synthesized the CoO nanorods along the[001]direction with a hexagonal crystalline structure.We adjusted the contents of water,the types of surfactant,the heating preservation time and cobalt precursor species in the reaction system and obtained CoO nanorods with two different crystal structures and morphologies.The morphology is relatively uniform only with the system contained cobalt stearate,1-octadecene and water.By combining infrared analysis and color changes of reaction process,we proposed the formation mechanisms of two CoO nanocrystals.(2)The research of magnetic properties showed that the c-CoO nanorods was antiferromagnetic and h-CoO nanorods was weakly ferromagnetic.Finally,the electrochemical property characterization of two kinds of CoO nanocrystals and the samples after annealing showed that the onset potentials decreased after annealing and Tafel slopes of samples decreased after annealing.Thus,we can draw a conclusion that the annealing process can promote the electric catalytic kinetics of CoO nanocrystals.