Synthesis And Electrochemical Properties Of Cobalt-based Metal Oxides And Their Complexes

At present,designing and synthesizing electrode materials with high-performance electrochemical properties is still an important research focus.Among many electrochemical electrode materials,Co3O4 has been extensively studied due to its high theoretical specific capacitance and good performance.However,the lower energy density limits its application as a kind of electrode material of supercapacitor.In order to solve this problem,reasonable modification of the Co3O4 nanostructures and the compounding of Co3O4 with other electrode materials are both desirable strategies.This thesis was based on the latter,Co3O4 was separately compounded with two kinds of binary metal oxides to obtain two kinds of composites of core-shell structure.It is well known that binary metal oxides have more efficient electrochemical activity than single metal oxides.This thesis used the hydrothermally synthesized Co3O4 nanowire arrays as the scaffold for anchoring binary metal oxides to obtain two kinds of binderless supercapacitor electrodes with higher specific capacitance and good cycle stability,which benefits from the synergistic effect of the two kinds of electrode materials.(1)Co3O4@Mn Co2O4 core-shell composite supported on nickel foam was synthesized via a facile hydrothermal process.When the reaction temperature was120 ? and the reactant concentration ratio was constant,by controlling the reaction time,samples with different morphologies were prepared and their electrochemical properties were studied.The sample prepared at 120 ? and 8 h showed an excellent electrochemical performance.At a current density of 1 m A cm-2,the specific capacitance of the composite could reach as high as 736.5 F g-1,which was nearly twice times than that of Co3O4 nanowires(370.67 F g-1).The above results showed that the electrochemical performance of the composite material with a core-shell structure has been greatly improved.At the same time,the composite also showed excellent cycling stability after 2000 cycles(81.59 % retention),indicating that the Co3O4@Mn Co2O4 composite is a kind of promising supercapacitor electrode material.(2)Co3O4@Ni WO4 core-shell composite was synthesized via a facile two-step hydrothermal method.When the reaction temperature was 130 ?,by controlling the reaction time and the concentration of reactants,the morphology of the product was adjusted.Through testing the properties of samples with different morphologies,the sample prepared at 130 ? and 8 h showed excellent electrochemical performance.At a current density of 1 m A cm-2,the specific capacitance could reach 612.83 F g-1,which was nearly 1.65 times than that of pure Co3O4 nanowires.Especially after 5000 cycles,the specific capacitance of the composite was still 1.59 times than the initial capacitance,which confirms that the composite has a remarkable electrochemical performance and can be used as a kind of electrode material for applications in the field of supercapacitor.