Multistage interface engineered cobalt polysulfides core-shell nanostructures for dual energy storage devices and hydrogen evolution
Feng Cao, Xue-Rong Shi, Peijie Wang, Wei Zhao, Mengru Huang, Jing Hu, Shusheng Xu, Guofeng Zhao, Guofeng Zhao
Abstract
Designing highly efficient electrode materials is one of the key issues for developing high performance energy storage devices and electrolytic hydrogen production . Herein, binder-free core-shell CoS x @CoNi 2 S 4 /CC nanocomposites were successfully prepared via calcination-sulfurization-electrodeposition using in-situ grown ZIF-67 nanorods as the precursor and self-sacrificial template. Attributed to the excellent electrical conductivity of the metal polysulfides core and CoNi 2 S 4 shell and the unique nanosheet/nanoflower morphology with multi-dimensional interfaces providing rich active centers and fast transport paths, the synthesized CoS x @CoNi 2 S 4 /CC not only presented excellent energy storage performance, but also delivered good activity toward hydrogen evolution reaction . The optimal CoS x @CoNi 2 S 4 -20/CC exhibited high capacities of 985 Cg −1 (i.e., 328.3 mA h g −1 ; capacitance of 1970 F g −1 ) at 1 A g −1 and excellent rate performance (92% capacity retention at 10 A g −1 ). Density-functional theory calculations reveal that the metal polysulfides presented great OH adsorption ability. The assembled CoS x @CoNi 2 S 4 /CC//AC hybrid supercapacitor and CoS x @CoNi 2 S 4 /CC//Fe supercapacitor-type battery showed high energy density (50 Wh kg −1 at 799 W kg −1 and 53.3 Wh kg −1 at 800 W kg −1 ) and cycle stability (about 81% of the initial specific capacity at 10 A g −1 after 6000 cycles).