Pyrolysis of cellulose: Correlation of hydrophilicity with evolution of functionality of biochar

Biochar is a carbonaceous material from pyrolysis of biomass, the application of which is governed by its various properties such as the distribution of the functionalities and the associated hydrophilic/hydrophobic nature. This study particularly focused on the correlation of functionalities of biochar with its polarities by conducting the pyrolysis of cellulose from 200 to 700 °C and the characterization of the biochar. The results demonstrated that -OH, instead of CO or C-O-C, played decisive roles in formation of the biochar with hydrophilic surface. The results showed that the maximum of -OH abundance and the aliphatic CH was reached at 440 °C. The significant transition of oxygen-rich functionalities to carbon-rich functionalities occurred in the temperature from 460 to 700 °C. The dominance of aromatization process above this temperature range resulted in the significant increase of hydrophobicity of the biochar. The hydrophilic surface was of importance for the use of biochar as support for promoting the dispersion of Cu in Cu/biochar by generating the bonding sites for chelating with Cu²⁺.