A Zinc Cobalt Sulfide Nanosheet Array Derived from a 2D Bimetallic Metal–Organic Frameworks for High-Performance Supercapacitors

Graphical MOF-templated electrode : A porous zinc cobalt sulfide nanosheet array on Ni foam (Zn-Co-S/NF) was constructed by growing 2D zinc/cobalt-based metal–organic framework (Zn/Co-MOF) nanosheets on NF, followed by additional sulfurization (see figure). The Zn-Co-S/NF nanosheet array was used directly as a supercapacitor electrode and showed much better electrochemical performance than zinc cobalt sulfide powder. An asymmetric supercapacitor was assembled from Zn-Co-S/NF and activated carbon electrodes, and its potential for practical application was demonstrated by driving a red LED. Porous ternary metal sulfide integrated electrode materials with abundant electroactive sites and redox reactions are very promising for supercapacitors. Herein, a porous zinc cobalt sulfide nanosheet array on Ni foam (Zn-Co-S/NF) was constructed by facile growth of 2D bimetallic zinc/cobalt-based metal–organic framework (Zn/Co-MOF) nanosheets with leaf-like morphology on NF, followed by additional sulfurization. The Zn-Co-S/NF nanosheet array acted directly as a supercapacitor electrode showing much better electrochemical performance (2354.3 F g −1 and 88.6 % retention over 1000 cycles) when compared with zinc cobalt sulfide powder (355.3 F g −1 and 75.8 % retention over 1000 cycles), which originates from good electrical conductivity and mechanical stability, abundant electroactive sites, and facilitated transportation of electrons and electrolyte ions due to the unique nanosheet array structure. An asymmetric supercapacitor (ASC) device assembled from Zn-Co-S/NF and activated carbon electrodes can deliver a highest energy density of 31.9 Wh kg −1 and a maximum power density of 8.5 kW kg −1 . Most importantly, this ASC also shows good cycling stability (71.0 % retention over 10000 cycles). Furthermore, a red LED can be powered by two connected ASCs, and thus as-synthesized Zn-Co-S/NF has great potential for practical applications.