Study On Characterization And Thermoelectric Properties Of Rice Husk Based Carbon Materials

Temperature difference power generation（also known as thermoelectric power generation）is a green power generation method,which can effectively convert low-grade energy such as solar energy,geothermal energy,industrial waste heat into electricity.Studies have shown that high output voltage and thermoelectric conversion performance can be obtained by using porous carbon materials（such as carbon nanotubes and nano-porous carbon）as electrode materials.Thermoelectric materials are the key factors to determine the thermoelectric performance and the selection and preparation of thermoelectric materials are the hot spot of current research on thermoelectric power generation.Compared with traditional metal materials,biomass carbon materials have higher specific surface area and have been used as thermoelectric materials in thermoelectric conversion.As a renewable biomass resource,rice husk is cheap.The preparation of carbon materials based on rice husk can help reduce the production cost of the temperature difference system and broaden the way of resource utilization of rice husk.Therefore,In order to produce rice husk based carbon material with high specific surface area,this paper will take rice husk biomass as raw material,from the aspects of material modification,rice husk char to activated carbon,to comprehensively study the rice husk based carbon material,so as to optimize the temperature difference system and increase the output voltage.In order to investigate the effect of hydrothermal pretreatment on the thermoelectric properties of rice husk char,the rice husk was modified by different hydrothermal temperatures,and its fuel characteristics were analyzed.The properties and microstructure of rice husk char were characterized by industrial analysis,elemental analysis,FTIR analysis and N₂adsorption.The specific surface area and total pore volume of rice husk char are increased after modification.The result demonstrates that the rice husk char with a specific surface area of 335.1 m²/g,the total pore volume of 0.173 cm³/g can be acquired when the hydrothermal temperature is 150℃.By using the rice husk chars as electrode and Na Cl solution as electrolyte,the output voltage of the modified chars is improved dramatically.At the temperature range of 50 K,the output voltage is 67.084 mv and the specific energy is106.7 m J/g,exhibiting the excellent thermoelectric conversion performance of modified rice husk char as a low-cost porous carbon.The results showed that the different activation temperatures and activator ratios had an important influence on the physicochemical properties of rice husk-based activated carbon.Under the activator ratios of 1:3 and the activation temperature of 800℃,the rice husk-based activated carbon reached the maximum specific surface area of 2935.3 m²/g and the maximum total pore volume of 1.7741 cm³/g.When the rice husk-based activated carbon prepared under this condition was used as electrode material,the voltage reached 122.41 mv,and the specific energy reached about 545.4 m J/g.After hydrothermal pretreatmen,the specific surface area and total pore volume of the rice husk-based activated carbon increased from 2935.3 m²/g to 3052.1 m²/g,and the total pore volume increased from 1.7741 cm³/g to1.8124 cm³/g.The output voltage increased from 122.41 mv to 133.43 mv,and the specific energy was about 600.6 m J/g,indicating that rice-husk-based activated carbon was an excellent electrode material for thermoelectric transformation.