Functional Materials Designed With Polysaccharide-derived Carbon Aerogel And Their Electrochemical Performance

Environmental pollution and energy crisis are important problems that need to be urgently solved.Biomass resources have renewability,which are able to solve the problem of unsustainable resources.Biomass-based materials are abundant,environmentally-benign,low-cost,biodegradable and biocompatible,and they can provide a "green" solution to the existing environmental and energy problems.In addition,biomass-based materials(especially polysaccharides)have abundant carbon content,which is a good choice for the preparation of carbon materials.Particularly,carbon aerogels have the advantages of lightweight,porosity and conductivity,showing great potential in supercapacitor electrodes.Consequently,it is of great significance to use biomass-based materials for the preparation of carbon arogels as supercapacitor electrodes.This work adopted TEMPO-oxidized cellulose nanofibers(TOCN)and cationic guar gum(CGG)to fabricate TOCN/CGG self-assembling hydrogels and subsequently transformed them into carbon aerogels via the freeze-drying and carbonization processes.The modulation of electrochemical properties of the carbon aerogels could be realized by adjusting the porous structure and composition of the carbon aerogels.First,TOCN/CGG self-assembling hydrogels were fabricated with TOCN and CGG of different concentrations,and they were finally turned into carbon aerogels.It was demonstrated that the lower the concentrations of TOCN and CGG,the more porous structure of the TOCN/CGG hydrogels.Furthermore,the corresponding carbon aerogels also showed better electrochemical properties.Specifically,the carbon aerogel obtained from the 1%TOCN/CGG hydrogel had a specific capacitance of 138.9 F/g.Secondly,the bacteria-containing waste water was found to improve the network stability of TOCN/CGG hydrogels.Moreover,the bacteria also showed benefit to the electrochemical properties of the corresponding carbon aerogels.The carbon aerogels obtained from the 1%bacteria@TOCN/CGG hydrogel had a specific capacitance of 218.9 F/g that was better than the other counterparts.Finally,other factors(i.e.the carboxylate content of TOCN,the ultrasonication treatment and liquid nitrogen treatment)are also of benefit to the improvement of structure stability of TOCN/CGG hydrogels.In this way,TOCN/CGG hydrogel of lower concentration could be made,which led to the hydrogels of higher porosity.Accordingly,the resultant carbon aerogels showed higher porosity and better electrochemical property.The liquid nitrogen treatment could also improve the electrochemical property of the corresponding carbon aerogels due to its influence on structure.This work demonstrated the methods to modulate the structure of TOCN/CGG hydrogels and disclosed the mechanism therein.Moreover,the carbon aerogels of abundant porosity were successfully manufactured.It was clarified the relation between the structure and electrochemical property of the TOCN/CGG hydrogel-derived carbon aerogels.These results might guide the future work on the structure design of polysaccharide-based hydrogels.It might also facilitate the research on the carbon aerogels from polysaccharide-based hydrogels.This work might inspire new ways for the value-added utilization of biomass mateirals,especially in the area of energy storage materials.