Transition metal assisted ionothermal carbonization of cellulose towards high yield and recycling

A sustainable natural polymer, cellulose, has been used as precursor for producing carbonaceous materials. Ionothermal carbonization (ITC) in ionic liquid (IL) could transform biomass into functional carbon materials at a relatively low temperature. In order to improve the ITC carbon yields and structures, the first raw transition metal chlorides were added into IL, 1-Butyl-3-methyl-imidazole chloride (BmimCl), and their catalyzing effects were compared. It is found that the catalyzing effects of transition metal chlorides are mainly correlated to their cation size. With the addition of 0.5wt% NiCl (based on IL), a high carbon yield of 94wt% is obtained. Additionally, the bio-based carbonaceous materials exhibit a higher graphitization degree with the addition of metal chloride. Furthermore, the IL shows good cyclability, and the carbon yield remains to be higher than 80 wt% after 5 cycles.