Generation of Graphene-like Carbon Materials Derived from Biomass Using Iron Species

Effective utilization of biomass and its conversion into valuable chemicals have attracted attention. We previously reported that industrial biomass residues were converted into graphene-like carbon materials (GLCs) with exceptional electrical conductivity through Fe(II)-coordination and heat processing under a low-oxygen atmosphere (Ishii. RSC Adv. 2021, 11, 18702−18707). In the present study, the effects of carbon sources on GLC formation were investigated using the following five pulp- and paper-production-related materials containing oxygen-functionalized aromatic structures: alkali lignin, humic acid, tannic acid, and the molecular analogues vanillic acid (VA) and gallic acid (GA). Addition of Fe(II) ions to the carbon sources successfully produced GLCs in all cases. GA and VA, which had high oxygen-containing functional group contents and low molecular weights, exhibited very efficient graphene formation across an Fe concentration range of 0.5–5 mmol/g. This suggests that carbon sources abundant in oxygen-containing functional groups can effectively coordinate to Fe(II) at high concentrations to facilitate graphene formation. Among the GLCs, those derived from GA and VA had the highest graphene yields and lowest defect densities. Catalysis by Fe0 and Fe3O4 facilitated dehydrogenation and carbon solubilization, which promoted graphene crystallization. This environmentally friendly method for biomass valorization into high-value carbon materials is a sustainable and efficient alternative to conventional graphene production methods.