The differential influence of biochar and graphite precursors on the structural, optical, and electrochemical properties of graphene oxide

This study investigates the synthesis and characterization of graphene oxide (GO) derived from two distinct precursors: graphite and pyrolyzed acacia wood sawdust via a modified Hummers method. As hypothesized, the commercial graphite-derived GO (GOG) exhibited a more ordered structure characterized by a well-defined diffraction peak with interlayer separation of 0.86 nm and crystalline order of 8.18 nm, consistent with extensive oxidation. Conversely, the biochar-derived GO (GOB) displayed a heterogenous structure with a less defined (001) plane and an emerging (002) plane corresponding to mixed hybridization states (sp2/sp3) and mixed crystallinity at different regions in the materials. Additionally, it retained excess aromatic carbons (C-H bond) on its basal plane increasing its disorderliness and defect density. As a result, despite the G bands showing greater incorporation of functional groups in GOG, GOB recorded a higher ID/IG ratio (0.95 vs. 0.93). By retaining a relatively higher proportion of sp2 domains, GOB demonstrated enhanced light absorption through additional electronic transmission evident by its lower bandgap energy (2.93) compared to GOG (4.20), extending absorption into the visible range. Its improved properties were further characterized by enhanced conductivity, surface area, porosity, and decreased charge transfer and ion diffusion resistance. The study emphasizes that the nature of defects and their distribution, influenced by the precursor material can influence GO properties than those predicted by oxidation levels alone. It opens a new pathway to exploring bio-precursors and their potential in tailoring the properties of GO for specific applications.