Metal-organic framework-derived Ni/ZnO nano-sponges with delicate surface vacancies as anode materials for high-performance supercapacitors

Ni/ZnO nano-sponges have been successfully synthesized through optimized annealing of Ni/Zn-based organic framework (Ni/Zn-MOF). The annealed MOF provides the stable carbon structure with 3D interconnection and prevents structural collapse during the charging and discharging process. The annealing causes the incorporation of intrinsic Ni³⁺ in the surface of NiO nanoparticles, providing more reaction active sites. The oxygen vacancies in ZnO and heterostructure interfaces between NiO and ZnO promote the charge transformation. Based on the aforementioned advantages, the Ni/ZnO nanocomposites exhibit excellent electrocatalytic performances for supercapacitors. The specific capacitance can reach to 807 F·g⁻¹ at 1 A·g⁻¹ in the studied electrodes. After 5, 000 cycles at 10 A·g⁻¹, the cyclic stability remains excellent at 86% of the initial capacitance. Moreover, the as-prepared asymmetric supercapacitor exhibits a high energy density of 30.6 W·h·kg⁻¹ at power density of 398 W·kg⁻¹. This study is expected to provide new insights into exploring the potential mechanism of catalyst action.