Figure 1: Morphology and elemental distribution of CM-NF electrodes.

(a) low-magnification s.e.m. image of the CM-NFs; (b) high-magnification s.e.m. image showing spherical morphology of CM-NF; (c) a s.e.m. image of CM-NFs, and the corresponding EDS elemental mappings of (d) carbon (red); (e) nitrogen (yellow); and (f) fluorine (purple). Scale bar, 15 μm (a), 1 μm (b) and 2 μm (c–f).