Assembly Of Lignin And Hemicellulose-Based Porous Functional Carbon Material And Its Application

Effective utilization of biomass resources has stimulated recent interests of researchers all over the world due to its excellent biodegradability,hydrophilicity,biocompatibility,and low price.In recent years,researchers begin to use biomass resources to replace traditional functional components.Herein,instructed by the function and taken the construction of structure as the main body,series of biomass-based porous functional carbon materials were fabricated.They would supplement the functional defects of original porous carbon materials and realize the high value applications of biomass resources.The main contents of this thesis were shown as follows.Lignosulfonate-modified graphene hydrogel(LS-GH)was synthesized through a one-step method.The three-dimensional(3D)porous architecture of graphene hydrogel was functionalized by lignosulfonate with diverse oxygen contained groups.Benefiting from large specific surface area,multiple porosity and sufficient active sites,the LS-GH adsorbent exhibited ultrahigh adsorption capacity(1210 mg g-1)for Pb(?)removal,far better than the pure graphene hydrogel(GH,385 mg g-1),which was among the highest in previous reported Pb(?)adsorbents.Importantly,the free-standing and flexible LS-GH can be used as a column-packed device,providing an efficient pathway for fast removal of Pb(II)with ultrahigh adsorption capacity of 1308 mg g-1 within 40 min.Furthermore,the LS-GH can be regenerated and reused after several recycled adsorption-desorption processes,and the adsorption capacities maintained?90%after 5 cycles and?82%after 10 cycle.A metal-free and flexible supercapacitor was fabricated based on lignosulfonate functionalized graphene hydrogels(LS-GHs).The mechanically strong LS-GHs can be directly used as self-supported electrodes without any other binder or additive.The Q/QH2 structure in LS could provide numerous redox active sites to increase the pseudocapacitance.It presents an impressive specific capacitance of 432 F g-1 in an aqueous electrolyte,which is nearly 2 times higher than that of a pure graphene hydrogel(238 F g-1).Moreover,the device exhibits high rate capability(81.0%capacitance retention at 20 A g-1)and cycling stability(90.0%capacitance retention over 10000 cycles).The resulting LS-GH electrodes are further fabricated into a flexible solid-state supercapacitor using H2SO4-polyvinyl alcohol(PVA)gel as the electrolyte.The integrated flexible device not only maintains high capacitive performances(408 F g-1 at 1 A g-1,75.4%capacitance retention at 20 A g-1 and 84.0%capacitance retention over 10000 cycles),but also exhibits excellent mechanical flexibility.A novel physically cross-linked hemicelluloses/graphene oxide(HC/GO)hydrogel was prepared through a green and facile self-assembling approach at ambient temperature.The formation of the hydrogels relies on the cross-linking effect of HC chains and the assembly of GO sheets.Owning to the relatively multiple and strong hydrogen bonding between HC and GO,the obtained HC/GO hydrogel has a well-defined 3D porous network and excellent mechanical properties.Meanwhile,HC/GO hydrogel exhibited pH-induced gel-sol transition,which suggested the composite hydrogel could be used to deliver the drugs and control them to be selectively released in the intestine(pH 6.8?7.4),reducing ineffectual release in the stomach(pH 1.5-2).More importantly,cellular toxicity test demonstrated that the HC/GO hydrogel was nontoxic and biocompatible for cells.Therefore,the physically cross-linked HC/GO hydrogel would be an attractive drug carrier for controlled drug release at physiological pH.Porous graphitic carbon was prepared through a hydrothermal method from hemicellulose and was activated by potassium ferrate(K2FeO4).Its electrochemical performace as electrode materials for supercapacitors was studied.During the activated process,K2FeO4 assisted the synchronous carbonization and graphitization of carbon.The Porous graphitic carbon possessed multiporous structure with large specific surface area(1250 m2 g-1).Electrochemical measurements revealed that the device exhibited high capacitive performances(262 F g-1)and cycling stability(95%capacitance retention over 10000 cycles).