(a)
(b)
(c)
(d)
Figure 9: (a) TEM image of the graphene dispersed by Nafion. (b) Zeta potential as a function of pH for Nafion-functionalized graphene and P25. (c) EIS of DSSCs with P25 and P25-graphene electrodes. The inset displays the Bode phase of two films. (d) Schematic diagram for energy band matching [156].