Study On Preparation Of Leather-based Porous Carbon Maliterial And Its Capacitance Performance

Nitrogen-doped porous carbon materials have been testified to have good performances in the fields of catalysis and energy storage.Therefore,the biomass nitrogen-rich precursors in nature as the raw materials taking the place of the chemical synthetic polymer precursors were applied to fabricating the nitrogen-doped porous carbon materials,which has the incomparable advantages.Moreover,as a kind of biomass processed from the animal fur,leather is mainly composed of collagen,which has a unique advantage in terms of nitrogen content.In the meantime,the traditional tanning industry is characterized by the low output and the heavy pollution,and it always converts a large amount of collagen into the solid wastes.Nevertheless,during the tanning process,the coordination bond between chromium salt and skin collagen is extremely fixed.Therefore,the traditional treatment cannot separate the collagen and the chromium in the solid wastes completely so as to generate a large quantity of the chromium-containing residues.But it is far more difficult to dispose non-hazardously the chromium-containing residues.Otherwise,the improper disposal will cause the secondary pollution.In this task,the preparation of activated carbon and its capacitive performance of the waste generated in the course of processing were studied due to its own ingredients and the structural characteristics of leather.First of all,regarding chrome tanned shavings as the research target,with the high-temperature carbonization and KOH activation,the activated carbon doped by nitrogen and with the larger specific surface area was prepared.Through optimizing the preparation process of the activated carbon,the electrochemical performances of the chrome-tanned shavings-based activated carbon was studied.Secondly,with chrome tanned shavings carbonized at the high temperature as an object,a method for dissolving the chromium oxide templates was proposed.In order to form the 3D porous structure on the carbon surface after dissolved chromium oxide,the layered activated carbon with the high specific surface area was further prepared by KOH activation,and the electrochemical performance of the layered porous carbon was investigated thoroughly.On the basis of the layered porous carbon prepared with the high specific surface area,nitrogen was doped with one-step hydrothermal method,so as to verify the synergistic action between the high specific surface area and the nitrogen content at a high proportion in the activated carbon on electrochemical energy storage.Taking the advantages of the 3D porous mesh structure possessed by the leather itself,the leather-based freestanding electrode plates doped by nitrogen were prepared through the high-temperature carbonization and the air activation,which further simplified the assembly and the preparation process of the supercapacitors,and evaluated the capacitive performances of the freestanding carbon sheet electrodes,which enriches and develops the application of leather solid wastes in the field of electrochemical energy storage and also has the remarkable social values for the resource utilization of the leather solid wastes.In addition,it provides the new views for developing the easy,economical and efficient electrochemical energy storage materials as well.On account of the above-mentioned research and experiment,the principal results are as follows:(1)Using chrome tanned leather shavings as the raw material,chrome tanned leather based porous carbon was prepared by carbonization and KOH activation.The specific surface area of porous carbon prepared by cherry blossom,saphorn shell,chrome tanned leather shavings,and sycamore bark And capacitance characteristics,screening chrome-tanned shavings-based porous carbon with a large specific surface area of 1745 m2 g-1 as a suitable raw material for the preparation of supercapacitors,using KOH as an activator,through a single factor experiment to study chrome-tanned shavings The activation conditions of carbon,when the alkali/carbon ratio is 2:1,the maximum specific surface area of the chrome-tanned leather-based porous carbon prepared is 2181 m2 g-1,the pore volume is 1.40 m3 g-1,and the oxygen content in the porous carbon It is 19.28%,the nitrogen content is 4.92%,and it has a partially graphitized structure(ID/IG=0.96).The electrochemical performance of supercapacitors made of chrome-tanned shale-based porous carbon shows that at a current density of 0.5 A g-1,porous carbon with an alkali/carbon ratio of 2 obtains a specific capacitance of 201.2 F g-1.And with excellent rate performance and excellent cycle stability,when the current density is 10 A g-1 after 5000 cycles,the specific capacity retention rate is 88.30%.(2)Taking chrome-tanned shavings-based porous carbon as the research object,a layered structure of porous carbon was prepared by dissolving chromium oxide template and activation.After chrome-tanned shavings were carbonized at 500?,the chromium oxide was distributed on the surface of the carbon material,Forming a carbon-chromium oxide composite,dissolving chromium oxide with potassium bromate to obtain a template carbon with a porous structure,and then activating with KOH,the unique structure of the template carbon gradually transforms into a layered porous structure with micropores,mesopores and macropores.Some oxygen and nitrogen impurity functional groups are well retained on the surface of the layered porous carbon.When the alkali/carbon ratio is 2,the maximum specific surface area of the prepared layered porous carbon is 3211 m2 g-1,and the pore volume is 2.02 cm3 g-1.The layered porous carbon has an oxygen content of 13.90%,a nitrogen content of 3.58%,and a partially graphitized structure(ID/IG=1.04).The capacitance performance of layered porous carbon shows that CTSHPC-2 has a high specific capacitance,good rate performance,low resistance and excellent cycle stability in a KOH solution with an electrolyte of 6 mol L'1.In particular,a layered porous carbon with an alkali/carbon ratio of 2 obtains a high specific capacitance of 318.4 F g-1 at 1 A g-1,even at a current density of 10 A g-1,after 5000 cycles,the specific capacitance It remained at 247 F g-1 with a retention rate of 93.50%.The results further prove that the layered porous carbon with an alkali/carbon ratio of 2 can be used as a potential electrode material for high-performance supercapacitors.(3)On the basis of the prepared high specific surface area layered porous carbon(CTSHPC-2),hydrothermal method was used to perform N-doping treatment on CTSHPC-2.Using SEM,TEM,BET,and XPS,it was found that urea was doped.It does not destroy the microstructure of layered porous carbon on a large scale,and when the ratio of urea to layered porous carbon is 15:1,the proportion of doped nitrogen content was the largest(6.21%).Nitrogen-doped layered porous carbon increased by 13%compared to the mean pore size from 2.51nm to 2.82nm.However,it was found that an excessively high percentage of urea content during the doping process would destroy the layered porous carbon.Structure of the prepared layered porous carbon with a high proportion of nitrogen doping and a high specific surface area in a three-electrode system electrolyte of 6 mol L'1 KOH,when the current density is 1.0 A g-1,the specific capacitance reaches 373.9 F g-1,However,as the current density increased from 1.0 to 20 A g-1,the capacitance retention rates were 70.80%,and when the current density was 10 A g-1,after 5000 cycles of charge and discharge,its the retention rate of the specific capacitance is about 88.40%.It shows good capacitance characteristics.(4)Using waste leather as a raw material and cutting it into circular slices,a nitrogen-doped leather-based free-standing carbon sheet was prepared by a high-temperature carbonization-air activation method,and the optimal carbonization temperature was determined to be 900?,The air activation temperature is 300?.According to the pore size distribution characterization,the specific surface area(386 m2 g-1)of carbon flakes was increased by 40.9%and the pore volume was 0.44 cm3 g-1.The average pore size is 4.6 nm.Tests in a three-electrode system had shown that the IR-drop of ALCS-300 at 1 A g-1 after air activation is reduced from 0.1257 V to 0.0970 V compared to LCS-900 before activation.When the current density is 0.5 A g-1,ALCS-300 obtains a specific capacitance of 136.5 F g'1.In addition,it has excellent cycle stability.After 5000 cycles at a current density of 1 A g-1 the specific capacity retention rate is 94.50%,which shows good performance.Without any additional adhesive,conductive agent and current collector,which reduces the assembly cost of the electrode and simplifies the assembly process of the capacitor.