液氮冷冻-真空解冻预处理木质素制备导电炭及其性能

Preparation and properties of conductive carbon from lignin pretreated by liquid nitrogen freezing-vacuum thawing

为了提高工业废弃生物质的附加值和进一步改善木质素高温热解炭的导电性能,笔者通过简单的液氮冷冻-真空解冻预处理结合高温碳化的方法将玉米秸秆中提取的酶解木质素制备成具有更高导电性能的木质素导电炭材料(PLC)。通过电阻率测试探究了不同碳化温度、碳化保温时间以及预处理时间对导电炭电阻率的影响,同时采用扫描电子显微镜、X射线衍射仪、X射线光电子能谱仪和拉曼光谱等测试手段对不同碳化保温时间下炭材料的石墨化程度以及导电性能进行了评价。结果表明:经过预处理后的木质素能够在高温条件下热解碳化形成石墨化程度更高、导电性更好的炭材料,在热解温度为1000℃、碳化时间为1 h时,PLC电阻率就能达到0.112Ω·cm。同时,PLC均为过渡态炭且含有少量氮元素,在高温条件下随着碳化保温时间增加,其无定形结构增加,有序性减小,导电性能和炭产率同步降低。因此,PLC能够充分地节省时间成本,从而提高工作效率。

As a new type of carbon material,biomass conductive carbon has attracted extensive attention in recent years because of its excellent conductive properties and environmental protection properties.Biomass conductive carbon materials have the characteristics of high conductivity,low resistivity,good electrochemical performance,and renewability.The high conductivity is due to the stability of covalent bonds between atoms in carbon materials,resulting in free conduction of electrons.The reason of low resistivity is that the carbon material has a very high electron density,which allows the current to be conducted well.Therefore,biomass conductive carbon materials have wide application prospects in energy,environmental protection,electronic devices,and other fields.As a natural renewable resource,lignin has received more and more attention.As a by-product of lignin pyrolysis,lignin pyrolysis carbon materials have the advantages of good adsorption performance,high specific surface area,good chemical stability,and low cost.Therefore,they have been widely used in environmental governance,energy storage and conversion,nanotech-nology,and other fields.As a kind of new material with development potential,the excellent performance characteristics of biomass conductive carbon materials provide a broad space for its future development and application,and also provide a new idea for the high value-added utilization of biomass resources.In order to improve the high value-added utilization of industrial waste biomass and further improve the conductivity of lignin pyrolytic carbon,the pretreated lignin carbon(PLC)with higher electrical conductivity was prepared by a high temperature carbonization method after a simple liquid nitrogen freezing-vacuum thawing pretreatment.The effect of different carbonization temperatures,carbonization holding times,and pretreatment times on the resistivity of conductive carbon were investigated using the resistivity tests.At the same time,the scanning electron microscope,X-ray diffraction,X-ray photoelectron spectroscopy,Raman tests,and other examination methods were used to evaluate the graphitization degree and electrical conductivity of carbon materials with different carbonization holding times.The results showed that the pretreated lignin can be pyrolyzed at high temperatures to form carbon materials with higher graphitization degree and better conductivity.When the pyrolysis temperature was 1000℃and the carbonization time was 1 h,the PLC resistivity could reach 0.112Ω·cm.At the same time,PLC is a kind of transitional carbon which contains a small amount of nitrogen.Under high temperature conditions,with carbonization holding time increasing,the amorphous structure increased,the ordered structure decreased inversely,and the conductivity and carbon yield decreased simultaneously.Therefore,PLC can fully save time and improve the working efficiency.