Fabrication And Characterization Of Cellulose-Based Superhydrophobic Materials And Electrode Materials

As the most abundant renewable polymer material on the earth,cellulose has the advantages of low price,environmental friendly,and good biocompatibility.How to turn cellulose into high value-added products is a significant research topic.The hydrophilicity and weak conductivity of cellulose limit its development in many fields,such as waterproof materials,adsorbent materials,and energy storage materials.In this study,cellulose-based hydrophobic materials and electrode materials are systematically studied.Superhydrophobic papers with a water contact angle of 168.5° are obtained by spraying hydrophobic nano-silica particles(SiO2 NPs)with a diameter of 10-20 nm on the surface of cellulose paper.The hydrophobic paper can retain the print visibility of original paper,because the particle size of SiO2 NPs is much smaller than the wavelength of visible light and Mie scattering is avoided.The papers exhibit self-cleaning property and excellent UV light resistance.This simple hydrophobic modification method is also applicable to other substrates such as fabrics,glass and wood.Trifluoroethyl methacrylate polymers are grfated onto the surface of cellulose paper by covalent bonding via surface initiated atom transfer radical polymerization(SI-ATRP).The introduction of low surface energy polymer greatly reduces the surface energy of cellulose.The hydrophobicity of obtained papers can be tuned by controlling the amount of the hydrophobic molecules and superhydrophobic papers with water contact angle up to 160°are obtained.The papers exhibit excellent resistance to UV light,excellent mechanical abrasion resistance,and can maintain superhydrophobicity after soaking in organic solvents for a long time.Nanocellulose suspension is obtained by combination of TEMPO catalytic oxidation and mechanical treatment.Aerogels with ultra-high porosity(?99.68%)and ultra-low density(?5.08 mg/cm3)are prepared from freeze-drying of the nanocellulose suspension.The aerogels are futher modified with silylating agent,resulting in a superhydrophobic and oleophilic nanocellulose aerogel with a water contact angle of 151.8°.The aerogel can selectively adsorb oil from a mixture of water and oil with excellent adsorption performance(260 g/g).The adsorption capacity for the organic solvent can reach,and it shows good performance.The aerogels can still maintain hydrophobicity and adsorption capacity after 30 adsorption-desorption,demonstrating its superior reusability.Superhydrophobic aerogels were fabricated by freeze-drying of silylated cellulose nanofibers and silica nanoparticles mixed suspensions.The as-prepared aerogels exhibited a hierarchical porous structure with pore diameters ranging from several nanometers to tens of microns,and the hierarchical rough structure as well as the low surface energy endowed the resultant aerogels with extremely high water contact angle up to 168.4°.Importantly,the composite aerogels could effectively separate surfactant-stabilized water-in-oil emulsions solely driven by gravity,with high separation efficiency(>99%)and high flux(1910±60 L m-2 h-1).We also assembled a simple device to collect oil directly from water-in-oil emulsions using the obtained aerogel and a self-priming pump.The fabrication of the composite aerogels in this work provides a versatile pathway to prepare cellulose-based materials for the highly effective separation of oil-water emulsions in practical applications.Nanocellulose/polypyrrole/silver composite aerogels were prepared by a simple dip-coating method using nanocellulose aerogel as template.The aerogels exhibit high compressive stress(128.9 kPa,60%)and good flexibility.The formation of silver particles and polypyrrole endow the composite aerogels with good electrical conductivity,and conductivity changes with the compressive strain.Considering its good flexibility and electrical conductivity,it can be used as a pressure sensor.Using the aerogel as an electrode material to assemble an all-solid-state supercapacitor,the supercapacitor exhibits a typical tantalum capacitor behavior.The supercapacitor shows a high specific capacitance value of 184 F/g at 1.0 A/g.Carbon nanosheets(CNS)obtained from hydrothermal and carbonization of glucose show a hierarchical porous structure and excellent electrochemical properties.The CNS-based supercapacitors show high specific capacitance of 225 F/g at 1.0 A/g and 87%retention at 10 A/g,as well as an excellent cyclic life of 98%initial capacitance after 20,000 cycles at 1 A/g.CNS is compounded with nanocellulose and polypyrrole to obtain a composite aerogel,which is assembled as an electrode material into an all-solid supercapacitor.The supercapacitors exhibit high specific capacitance of 368 F/g at 1.0 A/g as well as an excellent cyclic life of 85%initial capacitance after 20,000 cycles at 1 A/g.The reason for the increase of capacitance is that the addition of CNS not only improves the conductivity of the sample,but also facilitates the efficient transmission of electron/ion.