The XRD patterns of GO and RGO are shown in Fig. 2a. GO
has a large interlayer distance (0.8 nm, 2h = 10.3) due to the
formation of hydroxyl, epoxy, and carboxyl groups. After
reduction, the interlayer distance decreases to 0.375 nm
(2h = 23.4) due to the removal of some oxygen-containing
functional groups