  Since the strong interlayer interaction of AB-stacked graphene in bulk form
degrades the superior property of single-layer graphene, formation of randomly
stacked graphene is required to apply the high performances of graphene to
macroscopic devices. However, conventional methods to obtain bulk-scale
graphene suffer from a low crystallinity and/or the formation of a
thermodynamically stable AB-stacked structure. This study develops a novel
approach to produce bulk-scale graphene with a high crystallinity and high
fractions of random stacking by utilizing the porous morphology of a graphene
oxide sponge and an ultrahigh temperature treatment of 1500-1800 {\deg}C with
ethanol vapor. Raman spectroscopy indicates that the obtained bulk-scale
graphene sponge possesses a high crystallinity and a high fraction of random
stacking of 80%. The large difference in the random-stacking ratio between the
sponge and the aggregate samples confirms the importance of accessibility of
ethanol-derived species into the internal area. By investigating the effect of
treatment temperature, a higher random-stacking ratio is obtained at 1500
{\deg}C. Moreover, the AB-stacking fraction was reduced to less than 10% by
introducing cellulose nanofiber as a spacer to prevent direct stacking of
graphene. The proposed method is effective for large-scale production of
high-performance bulk-scale graphene.
