Colloidal Synthesis Of Niobium Disulfide Nanocrystals And Their Electrochemical Energy Storage Performance

Layered 2H-NbS2,a member of group-V transition metal dichalcogenides,has intrinsical metallic character owing to the half-filled 4dz2 orbital.The good electric conductivity,transparency,and preferable flexibility of 2H-NbS2 are practical for applications in energy storage.In this paper,2H-NbS2 nanosheets were synthesized via a colloidal synthesis method and employed as negative material for supercapacitor in neutral 1 M KCl aqueous solution.The main research contents and conclusions are as follows:(1)The morphologies of NbS2 nanosheets can be tuned through dynamics control.The lateral size,thickness,and structure of NbS2 nanosheets varied with the reaction temperature and the amount of CS2.Ultrathin,hierarchical and stacked NbS2 nanosheets were synthesized at 300? using 10,30,and 60 mmol CS2 as a sulfur source,respectively,and their lateral size was?3?m,700 nm,and 500 nm,and thickness increased from 10 nm,20nm to 60nm.(2)The growth mechanism of NbS2 nanosheets was studied.With the increase of reaction temperature,the lateral size and thickness of NbS2 nanosheets increased as the stability of the complexes reduced.Increasing the amount of CS2,the lateral size decreased and the thickness increased,owing to the diminishing for the critical size of NbS2 nanocrystals,and promotion for vertical growth of the anisotropic crystal.(3)The effect of structures of NbS2 nanosheets for electrochemical energy storage as negative electrode materials for supercapacitor was investigated.Ultrathin NbS2 electrode exhibits the highest rate capability due to the largest electrochemical surface area and efficient ion diffusion.While the hierarchical NbS2 shows the highest specific capacitance at low current densities(1?7 A g-1)for small charge transfer resistance,displays 221.4 F g-1 at 1 A g-1 and 117.1 F g-1 at 10 A g-1,and cycling stability with 78.9%of the initial specific capacitance after 10000 cycles.The aggregate or stacking of nanosheets can be suppressed effectively by constructing hierarchical structure NbS2 nanosheets.