Ultrathin porous Mn(PO3)2 nanosheets and MoO2 nanocrystal arrays on N, P-dual-doped graphene for high-energy asymmetric supercapacitors

Abstract Recently, heteroatom doped graphene based architectures exhibit promising prospects in the commercial application of supercapacitors because of their higher electrical conductivity and a wider potential window. Herein, we report on ultrathin porous nanosheets Mn(PO3)2 and MoO2 nanocrystal array on N, P dual-doped graphene (NPG) framework and study their supercapacitor properties. The irregularly overhead Mn(PO3)2 present a unique structure, which provide clear electron/ion transport channels to accelerate charge transfer together with the three-dimensional NPG structure. The obtained Mn(PO3)2/NPG hybrid electrode exhibit an extraordinary specific capacity (2073.4 F g-1, 1 A g-1) and good rate performance (capacity retention rate of 77.8 % from 1 A g-1 to 20 A g-1). In addition, the 3D NPG coated with MoO2 nanocrystal have also made a great progress in electrochemical performance of large capacitance and merely 5.54% fading capacitance after 10000 cycles. Subsequently, the asymmetric supercapacitor (ASC) hybrid devices based on Mn(PO3)2/NPG as the positive electrode and MoO2/NPG as the negative electrode has a wide voltage range of 0∼ 1.8V, delivers an excellent CF value of 213.8 F g -1 and keeps 91.5% initial capacitance retention after 10000 cycles. Furthermore, the as-prepared ASC also obtains an outstanding energy density of 96.2 W h kg -1 at a power performance of 726.73 W kg-1, which demonstrate that the reasonable conductive network of Mn(PO3)2/NPG // MoO2/NPG devices can greatly increase the utilization of active substances, improve the performance in all aspects and open up new avenues of the future application and development of supercapacitors.