Structural anisotropy in three dimensional macroporous graphene: A polarized XANES investigation

Three-dimensional macroporous graphene sponges with different densities were investigated by angular dependent carbon K-edge X-ray Absorption Near Edge Spectroscopy (XANES) with a linearly polarized beam. The C K-edge XANES analysis shows an unexpected anisotropic behavior of the macroporous graphene random networks. The macroporous graphene sponges expectedly show an exceedingly lower dichroic ratio compared with that of the highly oriented pyrolytic graphite, but spectra clearly points out the occurrence of oriented hexagonal carbon planes. The anisotropy of the investigated samples exhibits a linear dependence with the measured density. The XANES analysis supports the presence of graphene-like, two-dimensional planar structures inside these synthetic sponges and correlates it with different structural networks and/or density in graphene sponges.