Biochar as an Effective Alternative to Graphite for Graphene Oxide Synthesis

This study investigates the preparation of graphene oxide (GO) from biochar as a starting material. GO is a 2D carbon-based nanomaterial used in both its oxidized and reduced forms for applications in electronics, Li-ion batteries, biomedicine, and biosensing. It is produced through exfoliation and oxidation of graphite, which is classified among the European critical raw materials. In this work, graphite was replaced with biochar, the carbon-rich solid residue produced by biomass pyrolysis. Biochar is highly versatile, with properties that vary depending on its synthesis parameters. In this case, a graphite-like biochar is required, with high carbon content and extended conjugate domains. Slow pyrolysis was selected as a synthesis method. Specifically, considering 900 °C as pyrolysis temperature and licorice roots as biomass, different residence times were employed to investigate their influence on the C sp2 content of the product. Biochars prepared in 1 hour, 24 hours, and 48 hours were used for GO synthesis through the Hummers method. The resulting products were characterized through UV-Visible, Raman, and XPS spectroscopies and a comparison with GO prepared from graphite was performed to assess the suitability of biochar for this application.