Metal-carbide-assisted graphitization of biomass carbon and its impact on electrical and textural properties

Biomass-derived carbon is a sustainable precursor for the development of graphitic materials; however, its inherently amorphous structure limits both electrical conductivity and structural ordering. In this study, spruce bark was employed as a biomass precursor to investigate the catalytic roles of different metallic species Fe, B, and Mo in promoting graphitization and enhancing the physicochemical properties of hydrothermally carbonized carbon (HTC). X-ray diffraction (XRD) and Raman spectroscopy revealed that Fe and Mo catalysts facilitate the formation of metal carbides (Fe 3 C and Mo 2 C), which serve as transient intermediates that drive the growth of graphitic domains via a dissolution–precipitation mechanism. The degree of graphitization, indicated by the I D /I G ratio, decreased from 1.97 (HTC) to 0.79 (HTC-Mo), reflecting improved structural ordering. Electrical conductivity increased from 14 S cm −1 for HTC to 22 S cm −1 and 30 S cm −1 for HTC-Fe and HTC-Mo, respectively. Elemental analysis confirmed substantial deoxygenation, with the O/C ratio reduced from 0.49 to 0.03 in HTC-Mo. TEM imaging revealed well-developed graphitic layers surrounding Fe 3 C and Mo 2 C nanoparticles, corroborating their catalytic role in carbon reorganization. These findings demonstrate that Fe and Mo carbides significantly enhance the graphitization of biomass–derived carbon, improving both structural integrity and electrical conductivity, and offering a viable route for converting renewable biomass (spruce bark) into advanced conductive carbon materials.