Figure 2

(a) TEM image of GN sheet; (b) FESEM image of ACs; (c) SEM image of flexible GN/AC substrate; SEM images of GN/AC/MnO2 composite films prepared at various reaction times: (d) 300 s, (e) 600s, (f) 900s, (g) 1200s and (h) 1500s; (i) TEM image of GN/AC/MnO2-1200s composite films.