| Due to the eye-catching merits of short charging term, long lifespan and high power density, the novel energy device, which are known as supercapacitor, has shown the great potential in applications such as the grid, electrombiles and unmanned plane. According to the working mechanism, supercapacitors can be devided into two types: electrochemical double-layer supercapacitors(EDLC) and pesudocapacitors. Carbon materials are the most favorite electrode materials for the former while the metal oxides and conducting polymer are quite suit for the latter. For metal oxides, especially the bimetallic oxides, have higher specific capacitance and better stability than carbon materials and conducting polymer, respectively. Thus they have sparked worldwide research interest. Among these materials, Ni Mo O4 has been thought as one of the most promising electrode materials for pesudocapacitor, due to their low cost, high specific capacitance and environment friendly. However, the conductive of Ni Mo O4 is relatively poor and the particle is easily agglomerated for their magnetism, which in turns cause disappointing rate capability and cycling stability. Besides, Co Mo O4 is also well known because of the excellent rate capability and cycling stability,but the specific capacitance is not satisfactory. So it is of great importance to improve the rate capability and cycling stability of Ni Mo O4 or increase the specific capacitance of Co Mo O4. In this paper we focus on Ni Mo O4 and Co Mo O4 and chose sodium dodecyl sulfate(SDS)as surface active agent. The electrochemical properties of them were systematically studied and a compound of them was successfully synthesized which obtained multiple advantages of outstanding rate capability, cycling stability and high specific capacitance. The main results of this work are as following:1. SDS was used as surface active agent, and chemical co-precipitation method was used to synthesize Ni Mo O4?x H2 O nanorods. For comparison, another Ni Mo O4?x H2 O nanorods without using the SDS was also synthesized. The result reveals that the addition of SDS can avoid the agglomeration of Ni Mo O4?x H2 O nanorods effectively and the nanorods are expanded along the axes. SDS has also reduced the ohmic resistance of Ni Mo O4?x H2 O obviously and contribute a lot to the improvement of electrochemical performance. When the current density was 1 A?g-1,the specific capacitance of Ni Mo O4?x H2 O can be reach 1492.31 F?g-1, while the specific capacitance of the unmodified one can only be 1034.48 F?g-1.2. The same method was used to synthesize the Co Mo O4 nanorods. Again, the electrochemical performance greatly enhanced after modified by SDS. The test result showed that the specific capacitance was 276.49 F?g-1 when current density was 1 A?g-1. And even the current density increased to 20 A?g-1, the specific capacitance can still reach 220.05 F?g-1, with about 79.7% capacitance retention. Moreover, at the scan rate of 30 m V?s-1, the specific capacitance increased gradually up to 135.71% its original capacitance after 1000 cycles.3. By combining the advantages of Co Mo O4 and Ni Mo O4, the compound Co Mo O4-Ni Mo O4·x H2 O and SDS modified compound Co Mo O4-Ni Mo O4·x H2 O were synthesized by a facil chemical co-precipitation method. According to the experimental results, it was found that the modified Co Mo O4-Ni Mo O4·x H2 O demonstrated excellent electrochemical performance: a specific capacitance of 800.3 F?g-1 was achieved at current density of 1 A?g-1 and the maintenance of specific capacitance at scan current of 20 A?g-1 was 88.3%. What is worth noting is that after 1000 continuous CV cycles at a scan rate of 30 m V?s-1, about 93.2% of the maximum SC can still be retained. All of these information indicated that the modified compound Co Mo O4-Ni Mo O4·x H2 O possessed excellent cycle stability, relative high specific capacitance and good rate property. In conclusion, the modified Co Mo O4-Ni Mo O4·x H2 O was a promising electrode material for supercapacitors. |
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