Ultrathin Ti(3)C(2)T(x) (MXene) Nanosheet-Wrapped NiSe(2) Octahedral Crystal for Enhanced Supercapacitor Performance and Synergetic Electrocatalytic Water Splitting

Metal selenides, such as NiSe(2), have exhibited great potentials as multifunctional materials for energy storage and conversation. However, the utilization of pure NiSe(2) as electrode materials is limited by its poor cycling stability, low electrical conductivity, and insufficient electrochemically active sites. To remedy these defects, herein, a novel NiSe(2)/Ti(3)C(2)T(x) hybrid with strong interfacial interaction and electrical properties is fabricated, by wrapping NiSe(2) octahedral crystal with ultrathin Ti(3)C(2)T(x) MXene nanosheet. The NiSe(2)/Ti(3)C(2)T(x) hybrid exhibits excellent electrochemical performance, with a high specific capacitance of 531.2 F g(−1) at 1 A g(−1) for supercapacitor, low overpotential of 200 mV at 10 mA g(−1), and small Tafel slope of 37.7 mV dec(−1) for hydrogen evolution reaction (HER). Furthermore, greater cycling stabilities for NiSe(2)/Ti(3)C(2)T(x) hybrid in both supercapacitor and HER have also been achieved. These significant improvements compared with unmodified NiSe(2) should be owing to the strong interfacial interaction between NiSe(2) octahedral crystal and Ti(3)C(2)T(x) MXene, which provides enhanced conductivity, fast charge transfer as well as abundant active sites, and highlight the promising potentials in combinations of MXene with metal selenides for multifunctional applications such as energy storage and conversion. [Image: see text] ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s40820-019-0261-5) contains supplementary material, which is available to authorized users.