In this work, graphene materials have been prepared via thermal treatment of graphene oxides with the aid of intercalated nitric acid. The nitric acid not only favors the expansion of graphene but also facilitates the generation of pores into graphene. The specific surface area of such graphene frameworks is as high as 463 m(2)/g, and the pore volume reaches up to 2.23 cm(3)/g. When tested as supercapacitor electrodes, the graphene frameworks delivered an extremely high specific capacitance of ∼370 F/g while simultaneously maintained an excellent energy density of 12.9 Wh/kg and power delivery of 250 W/kg in aqueous electrolyte. These performances are much better than those of the control samples prepared without the aid of nitric acid. The porous structure and large specific surface area are believed to have contributed to the high performances.

Two series of well-defined lignin fractions derived from birch and spruce alkaline lignin (AL) by sequential solvent fractionation (i-PrOH-EtOH-MeOH) were engaged in a structure–property-application relationship study. The bacterial-derived alkaliphilic laccase (MetZyme) extensively catalyzed the oxidation and polymerization of AL fractions in an aqueous alkaline solution (pH 10). Lignin fractions with low molar mass reached a higher polymerization degree due to more phenolic-OH groups serving as reactive sites of oxidation and better lignin-laccase accessibility arose from a lower lignin condensation degree than the high molar mass ones. In comparison, AL fractions from spruce were found to be less reactive toward the laccase-catalyzed polymerization than those from birch, which was attributed to the much pronounced aryl-vinyl moieties’ oxidation. Furthermore, in situ polymerization of birch AL fractions using microfibrillated cellulose as a structural template was conducted in an aqueous medium and a dispersion of nanocellulose with its fiber network evenly coated by aligned lignin nanoparticles was obtained. The present study not only provides fundamental insights on the laccase-assisted oxidation and polymerization of lignin but also presents a new perspective for valorizing lignin in biobased fiber products through green processing of solvent fractionation and enzymatic treatment.

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Bisulfite pretreatment is a proven effective method for improving the enzymatic hydrolysis of empty fruit bunch (EFB) from oil palm for bioethanol production. In this study, we set out to determine the changes that occur in the structure and properties of EFB materials and fractions of hemicellulose and lignin during the bisulfite pretreatment process. The results showed that the crystallinity of cellulose in EFB increased after bisulfite pretreatment, whereas the EFB surface was damaged to various degrees. The orderly structure of EFB, which was maintained by hydrogen bonds, was destroyed by bisulfite pretreatment. Bisulfite pretreatment also hydrolyzed the glycosidic bonds of the xylan backbone of hemicellulose, thereby decreasing the molecular weight and shortening the xylan chains. The lignin fractions obtained from EFB and pretreated EFB were typically G-S lignin, and with low content of H units. Meanwhile, de-etherification occurred at the β-O-4 linkage, which was accompanied by polymerization and demethoxylation as a result of bisulfite pretreatment. The adsorption ability of cellulase differed for the various lignin fractions, and the water-soluble lignin fractions had higher adsorption capacity on cellulase than the milled wood lignin. In general, the changes in the structure and properties of EFB provided insight into the benefits of bisulfite pretreatment.

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