MOF-derived Ni-doped CoP@C grown on CNTs for high-performance supercapacitors

Abstract

A Ni-CoP@C@CNT nanocomposite was synthesized, in which Ni-doped CoP (Ni-CoP) were embedded in amorphous carbon matrix and then anchored on the surface of CNTs. The ZIF-67 derived Ni-CoP@C combined with the CNT skeleton, which rendered the composite with high specific surface area, rich interior porosity and continuous conductive network. This allows effective charge transfer, efficient buffering of interior stress, and therefore full exertion of the phosphide's pseudocapacitive performance. The Ni-doping was achieved by a facile solution-based ion exchange process of ZIF-67 at room temperature, which, according to the first principle calculations, was helpful to increase the ratio of free electrons in Ni-CoP to contribute to higher charge transmission behavior in electrochemical reactions. Due to the above characteristics, the Ni-CoP@C@CNT electrode exhibited a high specific capacitance of 708.1 F g−1 at 1 A g−1, which is almost fourfold compare to CoP@C (349.2 F g−1 at 1 A g−1). The ASC advice based on Ni-CoP@C@CNT can achieve a high energy density of 17.4 Wh kg−1 at the power density of 699.1 W kg−1 and excellent electrochemical cycling stability with a high capacitance retention of 117%. The Ni-CoP@C@CNT have great potential for the advanced energy storage devices.