Self-template synthesis of ZnS/Ni3S2 as advanced electrode material for hybrid supercapacitors

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In this work, ZnS/Ni3S2 electrode material was synthesized by a simple self-template approach. The synthetic route includes chemical precipitation of Zn–Ni precursor in a polyvinylpyrrolidone (PVP)/Milli-Q water solution by dropping ammonia solution and subsequent conversion of the Zn–Ni precursor to ZnS/Ni3S2via chemical reaction with thioacetamide (TAA), as the sulfur source. Here, the Zn–Ni precursor can be considered as a template that is converted to ZnS/Ni3S2 during the sulfidation process. The synthesized ZnS/Ni3S2 material displays a porous texture and a high specific surface area. These properties are beneficial for the investigation of the developed material as electrode in supercapacitors. Indeed, the obtained ZnS/Ni3S2 material exhibits improved specific capacity of 890.1 C g−1 at 1 A g−1 along with a good rate capability (70% retention of its initial value from 1 A g−1 to 20 A g−1). Furthermore, the ZnS/Ni3S2 electrode achieves a good cycling stability (∼82% retention of its capacity at 10 A g−1 after 6000 charging-discharging cycles). Moreover, ZnS/Ni3S2 is used as a positive electrode and porous reduced graphene oxide (PrGO) as a negative electrode to assemble a hybrid supercapacitor. The fabricated hybrid supercapacitor offers a specific capacity of ∼112.5 C g−1 at 0.5 A g−1, and delivers an energy density of 30.6 W h kg−1 at a power density of 880 W kg−1. This work not only demonstrates that ZnS/Ni3S2 material can serve as an efficient electrode material for supercapacitors, but also provides an easy operation way for preparing high performance metal-sulfide electrodes for energy storage application.