Stable Hierarchical Porous Heterostructure Ni 2 P/NC@CoNi 2 S 4 Fabricated via the NiCo-LDH Template Strategy for High-Performance Supercapacitors.

Transition metal phosphide/sulfide (TMP/TMS) heterostructures are attractive supercapacitor electrode materials due to their rapid redox reaction kinetics. However, the limited active sites and weak interfacial interactions result in undesirable electrochemical performance. Herein, based on constructing the NiCo-LDH template on Ni-MOF-derived Ni 2 P/NC, Ni 2 P/NC@CoNi 2 S 4 with a porous heterostructure is fabricated by sulfurizing the intermediate and is used for supercapacitors. The exposed Ni sites in the phosphating-obtained Ni 2 P/NC coordinate with OH - to in situ form an intimate-connected Ni 2 P/NC@NiCo-LDH, and the CoNi 2 S 4 nanosheets retaining the original cross-linked structure of NiCo-LDH integrate the porous carbon skeleton of Ni 2 P/NC to yield a hierarchical pore structure with rich electroactive sites. The conducting carbon backbone and the intense electronic interactions at the interface accelerate electron transfer, and the hierarchical pores offer sufficient ion diffusion paths to accelerate redox reactions. These confer Ni 2 P/NC@CoNi 2 S 4 with a high specific capacitance of 2499 F·g -1 at 1 A·g -1 . The NiCo-LDH template producing a tight interfacial connection, significantly enhances the stability of the heterostructure, leading to a 91.89% capacitance retention after 10,000 cycles. Moreover, the fabricated Ni 2 P/NC@CoNi 2 S 4 //NC asymmetric supercapacitor exhibits an excellent energy density of 73.68 Wh kg -1 at a power density of 700 W kg -1 , superior to most reported composites of TMPs or TMSs.