| Biomass has become a high quality raw material for the synthesis of carbon materials due to its wide source,abundant yield,environmentally friendly and renewable advantages.Moreover,the carbon materials prepared by renewable and low-cost biomass have the advantages of low price and large specific surface area,and can be used as adsorbents,catalysts,soil amendments,and so on.Transition metal oxides,with the advantages of low cost,environmental friendliness,and abundant reserves,are widely used in catalysis,electrochemistry,sensing,and magnetism.However,single transition metal oxide has disadvantages,such as low conductivity,easy agglomeration,and oxidation,which restrict their wide application.While carbon materials have the advantages of high surface area,high chemical stability,and good electrical conductivity,which can make up for the deficiency of transition metal oxide.In this paper,a series of biomass carbon/transition metal oxide composites were prepared by green and rapid synthesis method.The effects of different methods and preparation conditions on the physical and chemical characteristics of the composites were studied,and the potential applications of the composites in the fields of adsorption,catalysis,and electrochemistry were explored.What’s more,the synergistic mechanism between biomass carbon and transition metal oxides was also explored.It could provide experimental and theoretical basis for the synthesis and application of biomass carbon/transition metal oxide composites.The main research findings of this paper are as follows:(1)Using cellulose as the matrix,the microwave hydrothermal method combining controlled calcination conditions was used to selectively synthesize Fe3O4,γ-Fe2O3,and α-Fe2O3.The effects of different calcination conditions on the phase and adsorption properties of iron oxide were investigated.Fe3o4 was obtained in N2 atmosphere at 300℃ and 500℃.However,γ-Fe2O3 was obtained by calcining at 300℃ in air atmosphere,and α-Fe2O3 was obtained at 500℃.The synthesized composites showed excellent superparamagnetism of 17.6 emu g-1 and absorption performance of 51.04 mg g-1.And the adsorption rate of Fe3O4(N2,300℃)increased slowly until the adsorption equilibrium reached at 80 min.The γ-Fe2O3(Air,300℃)composite has the superparamagnetic properties of 17.6 emu g-1 and excellent adsorption properties of 51.04 mg g-1,and could achieve the maximum adsorption capacity of 98.72%within 120 min.(2)The cellulose-based ferrous precursors were synthesized by simple and environmentally friendly ultrasonic method.The study found that the different cellulose types had significant effects on phase,crystallinity,and morphology of Fe3O4/C nanocomposites.When CNC was used as raw material,the morphology of iron oxide in carbon composites is more regular.While the adsorption rate and adsorption rate of carbon composites obtained with MCC as raw material were better than CNC.The removal efficiency can reach 95.0%when the adsorption equilibrium.It has a bright prospect in the field of dye wastewater treatment.(3)Nanocellulose was used as the carbon source to prepare carbon/iron oxide nanocomposites by microwave hydrothermal method and subsequent high-heat calcination.Without surfactants and templates,the effects of different solvents on the preparation of carbon/iron oxide nanocomposites were investigated.In EG solution,the size of Fe3O4 nanoparticles was about 30-150 nn.When the EG/water mixed solvent was used,the morphology of the nanocomposite became an irregular ellipse.When water was used as a solvent,the polyhedron shape with a size of 300-5000 nm was obtained.The formation mechanism of iron oxide with different morphologies was also investigated.The adsorption process of MB followed the pseudo second-order reaction kinetics and the Freundlich isotherm model.The adsorption of MB was a multi-phase system,and after 3 cycles of regeneration,the removal efficiency was still stable above 70%,which had a good cycle stability for dye removal.At the same time,the adsorption mechanism was analyzed,the high adsorption capacity of carbon/iron oxide nanocomposites was determined by the large amount of hydroxyl groups on the surface of iron oxide and the high specific surface area of carbon materials.(4)Using lignin as carbon source,the N-doped lignin-based carbon nanofibers(CNFs)were successfully prepared by electrospinning and pyrolysis.The high content and uniform nitrogen blending of N-doped CNFs were prepared by adding urea and chemically polymerized aniline monomers.The N-doped CNFs had a uniform diameter of 3D network structure with a high specific surface area of 483 m2 g-1,which can provided more active sites and efficient ways of fast charge transfer for stable storage of charge.The CNFs/PANI/N-9 samples had a high specific capacitance of 199.5 F g-1(about four times the original CNFs)in the three electrodes,and CNFs/PANI/N-9 electrode exhibited excellent cycle stability,with 82%capacitance retention after 1000 cycles.What’s more,the mechanism of ion diffusion and charge transfer in n-doped CNFs with excellent electrochemical properties is also revealed.(5)A flexible porous C03O4-CNFs were prepared by electrospinning and subsequent carbonization.The addition of terephthalic acid increased the porosity and flexibility of CNFs.The porous CNFs network structure can shorten the electron path between the electrode and the electrolyte,and the doping of nitrogen and Co3O4 improved the conductivity of the samples.Under the synergy effect of CNFs and Co3O4,the porous Co3O4-CNFs/9 sample had a specific capacitance of 369 F g-1 at the current density of 0.1 A g-1,and the capacitance retention rate was the largest.The results indicated that porous Co3O4-CNFs had excellent electrochemical properties and potential applications for the development of high value-added biomass products.(6)The cellulose/CuO precursor was prepared by microwave-assisted ionic liquid method.The Cu,Cu2O,and Cu/Co2O composites with excellent photocatalytic properties were selectively synthesized by controlling different calcination temperatures.Under the synergistic effect of Cu2O and metallic copper and carbon materials,the recombination of photogenerated electron-hole pairs was inhibited.The Cu2O/C composites(800℃)had a removal efficiency of 99%after radiation for 5 h,and the reaction followed to the pseudo first-order kinetic model.The TOC value before illumination decreased from 16.44 mg L-1 to 9.85 mg L-1,indicating that the organic compounds were degraded to CO or CO2.This study provides a potential way for the preparation of carbon/metal(metal oxide)composites with biomass as the precursor.(7)Using cellulose as raw materials,the cellulose/ZnO composites were rapidly synthesized by microwave hydrothermal method.The cytotoxicity results showed that the cellulose/ZnO composites(0.06 M[Zn2+])had a cell viability of more than 95%.Subsequently,the ZnO/C composite was prepared using cellulose/ZnO composites as the precursors under the N2 atmosphere.The photocatalytic degradation efficiency of methylene blue(MB)and rhodamine B(RhB)dyes under ultraviolet and visible light irradiation was studied.The results showed that the degradation rates of MB and RhB were 99.67%and 55.61%,respectively,under UV irradiation for 240 min.The degradation efficiencies of MB and RhB dyes were 99.76%and 97.42%,respectively,when they exposed to visible light for 240 min.Based on the mechanism of synergistic effect of adsorption and photocatalytic of carbon materials,the photocatalytic performance of ZnO have improved.The research of the thesis,7 papers have been published in SCI international journals as the first author.It has been cited by others in SCI journals 39 times.The total IF of the published papers reached 28.2 as the first author.And the doctor candidate has been invited and involved in writing an English book for Elsevier.What’s more,8 invention patents has been applied,which 2 patents were authorized. |
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