Catalytic graphitization of biomass-derived ethanosolv lignin using Fe, Co, Ni, and Zn: Microstructural and chemical characterization

Bamboo has just recently emerged as a sustainable source of lignin extraction, paving the way for the development of sophisticated nano- and biomaterials based on lignin. Catalytic pyrolysis effectively synthesized graphitic carbon from biomass resources. This article investigates the influence of various metals (Fe, Co, Ni, and Zn) as catalysts in the catalytic graphitization of bamboo biomass-derived lignin. The graphitization process was carried out through thermal treatments conducted in a tightly closed muffle furnace at 1100 ℃ for a duration of 4 hrs. The metals-catalyzed graphitic carbons appeared flake-like microstructures under SEM with > 80 wt% graphitized carbon composition detected by XPS. Enhancement in the degree of graphitization, crystallite size, interlayer distance, and structural order was achieved within the order of Fe>Co>Ni>Zn. These are corroborated by XRD, indicating Fe-catalyst resulted in lignin graphite with a degree of graphitization of 92.07%, crystallite size (Lc) of 230.2 nm, and interlayer distances of 0.336 nm that are closer to commercial graphite. Raman revealed the Fe-catalysed lignin graphite has a lower defective ratio (ID/IG) of 0.55, while all graphitized lignin showed IG/I2D of > 1.0, indicating multiple layers of graphitic carbon. These findings might pave the way for future high-value graphite-based materials made from low-cost biomass, making it an intriguing prospect.