The development of new electrode materials with high specific capacity for excellent supercapacitive storage and energy conversion is highly desirable. The combination of metal and metal oxide with carbon is an effective strategy to achieve active bimetallic nanocatalysts. Herein, we developed a facile method to synthesize CoxMn1-xO@GC and Co/MnO@GC nanocomposites by an in situ conversion of Co-Mn PBAs. The as-prepared carbon hybrids, especially the resulting Co/MnO@GC carbonized under 700 °C (Co/MnO@GC-700), preserve the nanocubic morphology of Co-Mn PBAs and show excellent supercapacitance and OER performance. Specifically, an outstanding specific capacitance of 2275 F g-1 can be obtained with Co/MnO@GC-700 as the electrode material at a current density of 4 A g-1. When used as OER catalysts, Co/MnO@GC-700 shows a low overpotential of only 358 mV at 10 mA cm-2 in 1 M KOH. Moreover, a fabricated asymmetric supercapacitor device (ASC device), in combination with active carbon, shows a high cell voltage of 1.7 V and a considerably high specific capacitance of 246 F g-1 at 2 A g-1. Our nanoarchitecture design derived from PBAs provides a new opportunity for future applications in high-performance energy storage and transformation systems.
Mixed/composite oxides of transition metals with hollow structures, especially multishelled hollow architecture, have promising potential for different applications, but their syntheses still remain a big challenge. Herein, a facile coordination polymer precursor method was developed to construct various multishelled Zn-Mn-O hollow microspheres, including ZnMnO, ZnMnO, and ZnMnO/MnO. The composition of the hollow structures can be adjusted by controlling the composition of the coordination polymer precursors, which are easily obtained with Zn, Mn, and salicylic acid under solvothermal conditions. With a simple programmable heating process, the shell of the hollow structures can be adjusted and double-/triple-shelled ZnMnO, ZnMnO, and ZnMnO/MnO hollow microspheres have been controllably obtained. When the triple-shelled ZnMnO hollow microspheres are used as anode materials for lithium-ion batteries, excellent activity and enhanced stability can be achieved. The triple-shelled hollow ZnMnO exhibits a reversible capacity of 537 mA·h·g at 400 mA·g and a nearly 100% capacity retention after 150 cycles. This strategy is facile and scalable for the production of high-quality complex hollow nanostructures, with the possibility of extension to the preparation of other mixed metal oxides with complex structures.
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