Plasma-Assisted Synthesis of NiSe₂ Ultrathin Porous Nanosheets with Selenium Vacancies for Supercapacitor

Two-dimensional (2D) NiSe₂ nanosheets with porous ultrathin structure and selenium vacancies (NiSe₂ PNS_vac) are synthesized via plasma-assisted dry exfoliation for supercapacitor. The specific capacitance of the NiSe₂ PNS_vac is 466 F g^–1 in 1 M KOH electrolyte, which is much higher than those of NiSe₂ ultrathin nanosheeets (328 F g^–1) and NiSe₂ particles (251 F g^–1). After 1000 cycles, the specific capacitance of the NiSe₂ PNS_vac can be well-maintained, indicating its high cycling stability. The superior performance arose from its high conductivity, short electrolyte diffusion distance, and large specific surface area.