A novel hierarchic hydrothermal strategy to enhance the performance of nickel-cobalt metal-organic framework for supercapacitors

The study presents a novel hierarchical hydrothermal strategy, which can not only ensure the morphology characteristics of the initial hydrothermal products, but also enhance the properties of the materials. Here, the hierarchical hydrothermal treatment was carried out with bimetallic nickel cobalt metal organic framework (NiCo-MOF) as the representative. The results of characterization and electrochemical tests showed that NiCoMOF after hierarchical hydrothermal treatment (NCM-H) not only exhibits enhanced stability in crystal morphology but also an increased number of active sites in the material. At the same time, compared with the initial hydrothermal NiCo-MOF (NCM-F), the rate performance and cycle stability of NCM-H have been greatly improved. The prepared NCM-H electrode demonstrates a remarkable specific capacity of 1006F g- 1 at 1 A/g. Furthermore, the assembled NCM-H//AC asymmetric supercapacitor (ASC) device demonstrates a remarkable energy density of 100.8 Wh kg- 1 at a power density of 750 W kg- 1. Excellent rate performance (76.4 % retention from 1 A/g to 20 A/g) and cycling stability (83.8 % after 5000 cycles). This unique hierarchical hydrothermal strategy is convenient, efficient, environmentally friendly and low-cost, and can provide a meaningful reference for the performance improvement of MOF-based and other related materials.