Ultrathin N-doped Ti3C2-MXene decorated with NiCo2S4 nanosheets as advanced electrodes for supercapacitors

Abstract

An integrated system of heterostructure composites which can protect and optimize the structure and performance of single composition shows the positive signal of being interested in energy storage and conversion field. Recently, MXenes with versatile physicochemical properties are intriguing candidate materials for energy storage. Herein, by in situ nucleation and ion-exchange reaction, open NiCo2S4 nanosheets were intimately anchored onto the surfaces of ultrathin nitrogen-doped Ti3C2-MXene nanosheets (N-Ti3C2) to form the novel hierarchical N-Ti3C2/NiCo2S4 nanosheets. Furthermore, ultrathin N-Ti3C2 serves as a favorable conductive substrate not only to maintain structural stability, but also to afford the electrophilicity of electroactive centers and harmonize the electrochemical properties in multi-composition systems. On the other hand, NiCo2S4 nanosheets supply the effective channel for charge transport resulting in improved reaction kinetics and offer higher pseudocapacitance. Owing to the unique heterostructure and friendly interfacial interaction, the N-Ti3C2/NiCo2S4 electrode exhibits outstanding electrochemical performances with specific capacitance of 1849 F g−1 at 2 mV s−1, low internal resistance, excellent rate performance, and stable cycle life, which is much better than that of Ti3C2-MXene electrode. The results demonstrate that the heterostructure N-Ti3C2/NiCo2S4 was an advanced electrode, and this strategy provide the useful method to design MXenes-based electrode with superior electrochemical performance for supercapacitors.