Figure 3: TEM images of the Ni-Co-S-0.5

(a) and Ni-Co-S-3 (b), and hollow hetero-Ni-Co-S NBs (c). Schematic illustration for the transformation from core-shell structure to hollow NBs (d), HETEM images (e-g) and corresponding SAED pattern (h) of the as-fabricated hetero-Ni-Co-S NBs.