核壳结构ZIF-67@ZIF-8的制备及其超级电容性能研究

Preparation of core-shell structure ZIF-67@ZIF-8 and its supercapacitor properties

采用胶体化学合成法,在室温下使六水硝酸钴[Co(NO_(3))_(2)·6 H_(2)O]与2-甲基咪唑(MeIm)反应制备出ZIF-67,并将其作为湿种子,再通过原位生长法将二水乙酸锌(C4H_(6)O_(4)Zn·2 H_(2)O)与2-甲基咪唑(MeIm)生成的ZIF-8包裹在ZIF-67外,制备出核壳结构ZIF-67@ZIF-8材料,并用场发射扫描电镜(FE-SEM)、透射电镜(TEM)、X射线衍射(XRD)等方法对材料的形貌和结构进行表征。实验通过控制变量法改变原料金属离子的摩尔配比,得到不同配比下的样品,并将其制备成工作电极,在三电极体系下进行循环伏安法、恒流充放电法等电化学测试,结果表明,在原料金属离子(Co^(2+)与Zn^(2+))的摩尔比为1∶1时,制备出的材料在恒流充放电测试中电流密度为1 A/g时比电容为1144.4 F/g,具有较高的比电容以及较好的循环稳定性。

ZIF-67 was prepared by colloidal chemical synthesis with cobalt nitrate hexahydrate Co(NO_(3))_(2)·6 H_(2)O and 2-methylimidazole(MeIm)as raw material at room temperature,and it was used as wet seeds.ZIF-8 formed by zinc acetate dehydrate C4H_(6)O_(4)Zn·2 H_(2)O and 2-methylimidazole(MeIm)was coated around ZIF-67 by in-situ growth method to prepare the material of core-shell structure ZIF-67@ZIF-8.The morphology and structure of the synthesized materials were characterized by FE-SEM,TEM and XRD.The molar ratio of raw metal ions was changed by the control variable method,and the samples with different ratios were obtained.The obtained samples were selected as the active substance of working electrodes,and the electrochemical tests such as cyclic voltammetry and constant current charge and discharge were carried out in a three-electrode system.The results show that when the molar ratio of raw metal ions(namely Co^(2+)and Zn^(2+))is 1∶1,the prepared material has higher specific capacitance of 1144.4 F/g at the current density of 1 A/g and good cycling stability in constant current charge-discharge testing.