Structural, composition, optical, electrical, and electrochemical characterization of three-dimensional graphene foam

A comprehensive study is reported on two types of 3D graphene foam (GF) exhibiting distinct defect density, structural and functional properties. Wettability characterization demonstrates that high defect GF and low defect GF are hydrophilic, with a contact angle (CA) of approximately 14° and 72°, respectively. Optical characterization demonstrates close to zero reflectance and transmittance over a spectral range of 350 nm to 25 µm. X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDS) provide insight into chemical composition, defect density, and functionalization, while atomic force microscopy (AFM) shows that the high defect GF (HDGF) has a pronounced surface roughness, with a maximum surface roughness of over 18 nm. However the low defect GF (LDGF) exhibits a significantly smoother and more uniform surface with a maximum surface height of 4.5 nm. Electrochemical characterization demonstrates the impact of network connectivity on charge transport, highlighting differences in resistance and percolation thresholds between the two HDGF and LDGF foam types with areal capacitances of 38 and 32 µF cm^-2, respectively, at a current density of 0.1 mA cm^-2. The values show 90% and 94% retention of the initial capacitance when current density was increased 50-fold. A detailed structure-property-function relationship is established for the GF materials, useful for various applications.