Synthesis And Properties Of Biomass Carbon Microtubes

At present,most methods for preparing carbon nanotubes have the problems of cumbersome processes,severe synthesis conditions,and poor repeatability.On the one hand,most of its carbon sources are expensive and have a greater impact on environment.On the other hand,the relatively small diameter of carbon nanotubes also limits its application in certain fields,such as light-to-heat conversion and medium transfer.The carbon content of biomass is relatively high,which is one of the important carbon sources for the preparation of carbon materials.In view of the above problems,the solution system formed through the dissolution of biomass raw materials in ionic liquids acted as the carbon source to prepare carbon microtubes by direct carbonization in this study.The structure and properties of carbon microtube was regulated by optimizing the preparation parameters and introducing surfactants.The applications of carbon microtubes in electrochemical energy storage,solar photothermal conversion,photocatalysis and other fields were explored.The main research contents are as follows:1.The ionic liquid was used as a solvent to dissolve the biomass to form a solution system to synthesize carbon microtubes.The effects of reaction temperature,biomass type,and catalyst concentration on the structure and properties of biomass-based carbon microtubes were investigated.The results showed that the carbonization temperature and catalyst concentration played a decisive role in the formation of biomass carbon microtubes.When the carbonization temperature was 1200°C and the catalyst concentration was 0.25%,macroscopic aerogel-like and microscopic orderly arrangement can be obtained.The results of X-ray diffraction,Raman spectroscopy analysis and X-ray photoelectron spectrum indicated that carbon microtubes had a good graphitization structure and crystallinity,nitrogen doping was successfully realized.In addition,the graphitization degree decreased with the increase of catalyst concentration,and its specific surface area was up to 110.9 m² g^-1.The biomass carbon microtube loaded with Mn O₂ can be used as electrode material for supercapacitors.The three-electrode test system was used to test the capacitance performance of the Mn O₂/carbon microtubes composites.At a current density of 250 m A g^-1,the specific capacitance can reach 254.3 F g^-1,which showed a promising rate performance.The composite aerogel prepared from biomass carbon microtubes and nanocellulose had excellent solar-thermal conversion performance.Under the light intensity of 1 k W m^-2,the water evaporation rate was 1.33 kg m^-2 h^-1,and the thermal conversion efficiency can reach 86.7%.The thermal conversion efficiency can reach 74.8%under simulated seawater conditions.2.The influence of surfactant on the morphology and structure of biomass carbon microtubes was also studied.The physicochemical properties and morphology of biomass-based carbon microtubes prepared under different conditions were studied by means of X-ray diffractometer,Raman spectrometer and scanning electron microscope.The results showed that different surfactants had different effects on the structure of CMTs,where the cationic surfactant CTAB significantly increased the tube formation temperature.At certain concentrations,the biomass carbon microtubes were broken.The anionic surfactant CMC can form carbon microtubes with relatively small diameters,and with the change of its concentration,the morphology and structure of biomass carbon microtubes changed from forming orderly to breaking.The capacitive properties of carbon microtubes were tested,and the specific capacitance of the material can be obtained in the electrochemical test.The modified carbon microtubes loaded with bismuth bromide,and the composite aerogels prepared with nanocellulose and carbon microtubes had excellent dual properties of solar photothermal conversion and photocatalysis.Under light intensity of 1k W m^-2,the water evaporation rate was 1.47 kg m^-2 h^-1,and the heat conversion efficiency can reach 91.1%.Simultaneously,the high-efficiency organic dye catalytic degradation was also completed,and the degradation rate can reach 94.7% in 60 minutes.