Co3O4/ZnO nanoheterostructure derived from core shell ZIF 8@ZIF 67 for supercapacitors
In this work, we developed a novel and facile method to fabricate a Co3O4/ZnO nanoheterostructure via a solid solid conversion process using core shell MOFs@MOFs as a template and source of cobalt and zinc. Herein, we set out to prepare core shell structured ZIF 8@ZIF 67, which consists of ZIF 8 [Zn(MeIm)2]n) (MeIm 2 methylimidazole) as the core and ZIF 67 [Co(MeIm)2]n) as the shell, through a seed mediated growth method. Co3O4/ZnO nanoheterostructure was prepared through the thermal conversion of core shell ZIF 8@ZIF 67. This hierarchical Co3O4/ZnO exhibits a high specific capacitance of 415 F g 1 at 0.5 A g 1 and an improved rate capability (93.2% retention at 10 A g 1) Asymmetric supercapacitors were fabricated using the Co3O4/ZnO heterostructure as the positive electrode and active carbon as negative electrode. The operation voltage is expanded to 1.4 V in aqueous electrolyte, revealing an energy density of 43.2 W h kg 1 at a power density of 1401 W kg 1. This MOF driven strategy can be expanded to the preparation of other metal oxide nanoheterostructures by varying the type of MOFs, and may find potential application in high performance supercapacitors.