Design and synthesis of 3D Co3O4@MMoO4 (M=Ni, Co) nanocomposites as high-performance supercapacitor electrodes

Recent attentions have been focused on the synthesis and application of nanocomposites for supercapacitors, which can have superior electrochemical performance than single-structured materials. Here we designed and synthesized three-dimensional (3D) Co3O4@MMoO4 (M = Ni, Co) nanocomposites on Ni foam, which combined separately the advantages of the good rate capability of Co3O4 and the high specific capacitances of MMoO4 (M = Ni, Co), and the materials have shown surprising specific capacitances (2041 F g−1 of Co3O4@NiMoO4 and 857 F g−1 of Co3O4@CoMoO4 at a current density of 0.5 A g−1) and excellent cycling stability (72% capacitance retention of Co3O4@NiMoO4 and 100% capacitance retention of Co3O4@CoMoO4 after 3000 cycles). To enhance energy density, the asymmetric supercapacitors were assembled where Co3O4@MMoO4 (M = Ni, Co) and activated carbon (AC) acted as the positive and negative electrodes, respectively. The maximum specific capacitance (128 F g−1 of AC//Co3O4@NiMoO4 and 105 F g−1 of AC//Co3O4@CoMoO4) and the specific energy 41.9 Wh kg−1 of AC//Co3O4@ NiMoO4 and 38 Wh kg−1 of AC//Co3O4@CoMoO4) are demonstrated for a cell voltage between 0 to 1.6 V, exhibiting a high energy density and stable power characteristics.