Supercapacitors, as one of most popular power storage devices, present high power density, rapid charge-discharge rates and long cycle life. The crucial part of such devices is electrode materials. Low-cost MnO2 nanoparticles, together with other desirable advantageous features, such as nature abundance and environmental compatibility, offer exciting opportunities in the development of energy storage devices. However, the electrochemical performance of the pure nanostructured MnO2 still cannot meet the requirement of high energy or power density and long-time cyclic life. In recent years, one of the most powerful and facile approaches is to assemble MnO2 nanoparticles with graphene, for its high conductivity and specific surface area. These characteristics contribute to improve the conductivity and reduce the volume expansion. To further enhance the binding force between MnO2 nanoparticles and graphene and improve the electrochemical stability, embedding graphene with nitrogen atoms, is a promising and simple approach. As it is known, the capacitance performances of MnO2 nanoparticles decrease with increasing crystalline nature. Therefore, finding a facile routine and choosing a suitable temperature to achieve the controllable synthesis of weakly crystallized MnO2 nanoparticles and nitrogen doped graphene hybrids is significant for the development of supercapacitors. Professor Long Zhang and Mr. Jun Mei proposed a facile and economic method to synthesize MnO2/nitrogen doped graphene hybrids (MnO2/N-RGO) with ammonia pretreatment. Compared with MnO2/graphene hybrids (MnO2/RGO), the novel hybrids show enhanced electrochemical performances. At a current density of 2.0 mA cm-2, the capacitance of as-obtained hybrids was up to 275.2 F g-1 and retained 98.3% of initial capacitances after 1000 cycles. These results illustrate that ammonia pretreatment is effective for nitrogen atom doping (a level of 3.73%) and the hybrids are potential as electrode materials for supercapacitors. More importantly, this controllable method is convenient for scalable application and provides an example for synthesis of other metal oxides nanoparticles and nitrogen doped graphene hybrids.
Jun Mei, Long Zhang,
Jilin Provincial Engineering Laboratory for the Complex Utilization of Petro-Resources and Biomass, Changchun University of Technology, Changchun, 130012, PR China.
Nanostructured MnO2/nitrogen doped graphene (MnO2/N-RGO) hybrids were synthesized by a facile and economic method at low temperature with ammonia pretreatment. Characterizations show nitrogen atoms were embedded into graphene lattice during pretreatment followed by MnO2 nanowires anchored onto graphene flakes. Compared with MnO2/graphene (MnO2/RGO) hybrids, the novel hybrids exhibited higher capacitance value and enhanced cyclic stability. At a current density of 2 mA cm−2, the capacitance of as-obtained hybrids was up to 275.2 F g−1 and retained 98.3% of initial capacitances after 1000 cycles. These results illustrate that ammonia pretreatment is effective for nitrogen atom doping and the hybrids are potential as electrode materials for supercapacitors.Go To Electrochimica Acta