多級孔道結構的稻殼基電容炭材料的制備及其電容性能研究
發(fā)布時間：2018-07-29 10:18
【摘要】：超級電容器因其具有功率密度大、循環(huán)壽命長、充放電效率高等特點，近年來引起了人們的廣泛關注。電極材料作為超級電容器的重要部分是決定超級電容器性能的關鍵。具有多孔結構的活性炭材料具有成本低廉、比表面積高、來源廣泛等優(yōu)點，目前被廣泛應用于超級電容器電極材料。 利用稻殼為前驅體制備用于超級電容器的活性炭（電容炭）已經成為一個研究熱點。但目前稻殼基活性炭（Rice Husk based activated Carbon, RHC）存在著電容性能不理想、制備成本高且污染環(huán)境等問題，限制了RHC在超級電容器中的應用。本文以實現(xiàn)稻殼基電容炭在超級電容器中的應用為目標，，以稻殼為原料，通過化學活化法制備了具有不同孔道結構的稻殼基電容炭材料，研究了制備條件、稻殼的結構、組成與活性炭的孔結構及其電容性能的內在聯(lián)系，研究了RHC在酸性和堿性電解質溶液中的穩(wěn)定性，探究了RHC在堿性電解質溶液中的衰減機理，并提出了提高其循環(huán)壽命的新方法，設計了稻殼基電容炭的綠色制備工藝，主要研究成果如下： （1）利用稻殼的自身模板結構，通過炭化、堿煮、活化制備出了具有高比表面積的稻殼基多級孔道活性炭（Rice Husk based Hierarchical Activated Carbon,RHHAC），并研究了多級孔道結構的形成機理。RHHAC的表層為三維多孔結構，內部為平行排列大孔通道，在通道壁上同時存在大孔和大量的微介孔。所制得的RHHAC在6mol L-1KOH中表現(xiàn)出優(yōu)異的電化學性能。電流密度為0.5A g-1時，其比電容為278F g-1。當電流密度由0.5A g-1增大到20A g-1時，其電容保持率為77.2%，表現(xiàn)出較好的倍率特性。由其構成的對稱型超級電容器，當功率密度為6195W kg-1時，其能量密度仍保持7.4Wh kg-1，是非常有前景的高性能超級電容器電極材料。 （2）研究了稻殼中SiO2對KOH活化過程中孔結構形成的影響。結果表明，未去除稻殼中的SiO2時，所制備的活性炭具有較多微孔；去除稻殼中的SiO2時，活性炭具有介孔、大孔較多。這是由于KOH活化過程中SiO2優(yōu)先與KOH反應形成K2SiO3，K2SiO3的形成阻礙了KOH對稻殼的上下表皮的活化，同時造成中部的維管束活化過度導致結構破壞，導致介孔形成和擴大以及大孔的形成受阻。 （3）研究了RHC在KOH和H2SO4中的循環(huán)特性。結果表明，RHC在H2SO4中表現(xiàn)出優(yōu)異的穩(wěn)定性，而在KOH中穩(wěn)定性較差。這是由于在超級電容器循環(huán)充放電過程中含氧官能團在兩種電解質中發(fā)生不同的反應引起了正極電極電勢的變化差異，從而導致RHC作為超級電容器在兩種電解質中的循環(huán)穩(wěn)定性發(fā)生變化。在KOH電解質中，羧基和內酯基團發(fā)生水解反應產生的靜電排斥和空間位阻效應使得正極電容下降，引起正極電勢的增加和正極氧化，從而導致循環(huán)壽命的衰減。在H2SO4電解質中，含氧官能團發(fā)生可逆的氧化還原反應并不引起正極電勢的正移�；赗HC在KOH電解質溶液中衰減過程的研究，通過熱處理去除RHC表面含氧官能團，使得其循環(huán)穩(wěn)定性得了大大提升，10000次恒流充放電后的電容保持率由熱處理之前的28.3%提升至94.7%，但熱處理后材料的比電容降低了30%；提高正負極的質量比抑制了正極電勢的正移，改善了RHC在KOH中的循環(huán)穩(wěn)定性，當正負極質量比由最初的1：1提高到2：1時，10000次恒流充放電后電容保持率由最初的28.3%提升至95.3%，電容降低了12%。通過提高正負極質量比的方式來改善RHC在KOH中的循環(huán)穩(wěn)定性，相對于熱處理具有操作簡單、易于實現(xiàn)的特點。 （4）基于稻殼基電容炭的制備，提出了兩種綠色制備工藝。在高比電容稻殼基活性炭綠色制備工藝中，將RHC制備過程中產生的廢液經酸化和電解之后，獲得了納米SiO2，并可實現(xiàn)活化劑KOH和水的循環(huán)利用。相對于普通制備工藝，具有成本低、綠色環(huán)保的特點。在稻殼基多級孔道活性炭綠色制備工藝中，利用石灰乳將RHHAC制備過程中產生的廢液轉化為活化劑KOH，實現(xiàn)活化劑KOH和水的循環(huán)利用。
[Abstract]:Because of its high power density, long cycle life and high charging and discharging efficiency, supercapacitor has attracted wide attention in recent years. As an important part of supercapacitor, the electrode material is the key to determine the performance of supercapacitor. The porous structure of activated carbon material has low cost, high surface area and wide source. These advantages are widely used in electrode materials of supercapacitors.
Using rice husk as a precursor to prepare active carbon for supercapacitor (capacitor carbon) has become a hot spot. But at present, the Rice Husk based activated Carbon (RHC) has the problems of low capacitance performance, high preparation cost and pollution environment, which restricts the application of RHC in supercapacitor. The application of rice husk based capacitance carbon in supercapacitor was taken as the target. Rice husk based capacitor carbon materials with different pore structure were prepared by chemical activation method. The preparation conditions, the structure of rice husk, the structure of the rice hull and the pore structure of activated carbon and its capacitive energy were studied. The acid and basic electricity of RHC were studied. The stability of the solution in the solution was solved, and the attenuation mechanism of RHC in alkaline electrolyte solution was explored. A new method to improve its cycle life was proposed. The green preparation technology of rice husk based capacitor carbon was designed. The main research results were as follows:
(1) using the self template structure of rice husk, by carbonization and alkali cooking, the Rice Husk based Hierarchical Activated Carbon, RHHAC, which has high specific surface area, is prepared, and the formation mechanism of the multistage channel structure is studied. The surface of.RHHAC is three-dimensional porous structure, and the interior is parallel to the large pore channel. There is a large pore and a large number of micro mesopore on the channel wall. The obtained RHHAC shows excellent electrochemical performance in 6mol L-1KOH. When the current density is 0.5A g-1, its specific capacitance is 278F g-1. when the current density increases from 0.5A g-1 to 20A g-1, and its capacitance retention rate is 77.2%, showing a better multiplier characteristic. The symmetry of the current density is symmetrical. When the power density is 6195W kg-1, the energy density of the super capacitor is still 7.4Wh kg-1. It is a very promising electrode material for high performance supercapacitors.
(2) the effect of SiO2 on the formation of pore structure in the activation process of KOH in rice husk was studied. The results showed that the activated charcoal prepared by the SiO2 in the rice husk had more micropores. When the SiO2 in the rice husk was removed, the activated carbon had mesoporous and large pores. This was due to the formation of K2SiO3 and the formation resistance of K2SiO3 in the process of KOH activation and the reaction of SiO2 to KOH. The activation of the upper and lower epidermis of the rice hull was hindered by KOH, and the excessive activation of the vascular bundles in the central region resulted in structural damage, which resulted in the formation and expansion of mesoporous and the formation of the macropores.
(3) the cyclic characteristics of RHC in KOH and H2SO4 are studied. The results show that RHC shows excellent stability in H2SO4 and is not stable in KOH. This is due to the difference in the change of the positive electrode potential by the different reactions of oxygen functional groups in the supercapacitor during the cycle charge and discharge process, which leads to RH. The cyclic stability of the C as a supercapacitor in the two electrolytes is changed. In the KOH electrolyte, the electrostatic repulsion and the space hindrance effect produced by the hydrolysis of the carboxyl and lactone groups make the positive pole capacitance decrease, cause the increase of the positive pole potential and the positive pole oxidation, and lead to the decay of the cycle life. In the H2SO4 electrolyte, The reversible oxidation reduction reaction of the oxygen functional group does not cause the positive shift of the positive electrode potential. Based on the study of the decay process of the RHC in the KOH electrolyte solution, the oxygen functional groups on the RHC surface are removed by heat treatment, which makes the cycle stability greatly improved. The capacity retention of the 10000 constant current charge discharge is 28.3% before the heat treatment. Up to 94.7%, but the specific capacitance of the material is reduced by 30% after heat treatment; the mass ratio of the positive and negative pole increases the positive shift of the positive pole potential, and improves the cyclic stability of RHC in KOH. When the positive and negative mass ratio is increased from the original 1:1 to the 2:1, the capacity holding rate of the 10000 constant current charge discharge is raised from the initial 28.3% to 95.3%, and the capacitance is reduced. 12%. improves the cycle stability of RHC in KOH by improving the ratio of positive and negative mass ratio, which is simpler and easier to implement than heat treatment.
(4) based on the preparation of rice husk based capacitance carbon, two green preparation processes were put forward. In the preparation process of high specific capacitance rice husk based activated carbon, the waste liquid produced in the process of RHC preparation was obtained after acidification and electrolysis, and the nano SiO2 was obtained, and the activating agent KOH and water could be used in the circulation. Compared with the common preparation process, the cost was low. In the green preparation process of the multi-stage channel active carbon in the rice husk base, the waste liquid produced in the process of RHHAC preparation is converted into activator KOH by using lime milk to realize the recycling of activator KOH and water.
【學位授予單位】：吉林大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：TQ127.11;TM53
本文編號：2152363
[Abstract]:Because of its high power density, long cycle life and high charging and discharging efficiency, supercapacitor has attracted wide attention in recent years. As an important part of supercapacitor, the electrode material is the key to determine the performance of supercapacitor. The porous structure of activated carbon material has low cost, high surface area and wide source. These advantages are widely used in electrode materials of supercapacitors.
Using rice husk as a precursor to prepare active carbon for supercapacitor (capacitor carbon) has become a hot spot. But at present, the Rice Husk based activated Carbon (RHC) has the problems of low capacitance performance, high preparation cost and pollution environment, which restricts the application of RHC in supercapacitor. The application of rice husk based capacitance carbon in supercapacitor was taken as the target. Rice husk based capacitor carbon materials with different pore structure were prepared by chemical activation method. The preparation conditions, the structure of rice husk, the structure of the rice hull and the pore structure of activated carbon and its capacitive energy were studied. The acid and basic electricity of RHC were studied. The stability of the solution in the solution was solved, and the attenuation mechanism of RHC in alkaline electrolyte solution was explored. A new method to improve its cycle life was proposed. The green preparation technology of rice husk based capacitor carbon was designed. The main research results were as follows:
(1) using the self template structure of rice husk, by carbonization and alkali cooking, the Rice Husk based Hierarchical Activated Carbon, RHHAC, which has high specific surface area, is prepared, and the formation mechanism of the multistage channel structure is studied. The surface of.RHHAC is three-dimensional porous structure, and the interior is parallel to the large pore channel. There is a large pore and a large number of micro mesopore on the channel wall. The obtained RHHAC shows excellent electrochemical performance in 6mol L-1KOH. When the current density is 0.5A g-1, its specific capacitance is 278F g-1. when the current density increases from 0.5A g-1 to 20A g-1, and its capacitance retention rate is 77.2%, showing a better multiplier characteristic. The symmetry of the current density is symmetrical. When the power density is 6195W kg-1, the energy density of the super capacitor is still 7.4Wh kg-1. It is a very promising electrode material for high performance supercapacitors.
(2) the effect of SiO2 on the formation of pore structure in the activation process of KOH in rice husk was studied. The results showed that the activated charcoal prepared by the SiO2 in the rice husk had more micropores. When the SiO2 in the rice husk was removed, the activated carbon had mesoporous and large pores. This was due to the formation of K2SiO3 and the formation resistance of K2SiO3 in the process of KOH activation and the reaction of SiO2 to KOH. The activation of the upper and lower epidermis of the rice hull was hindered by KOH, and the excessive activation of the vascular bundles in the central region resulted in structural damage, which resulted in the formation and expansion of mesoporous and the formation of the macropores.
(3) the cyclic characteristics of RHC in KOH and H2SO4 are studied. The results show that RHC shows excellent stability in H2SO4 and is not stable in KOH. This is due to the difference in the change of the positive electrode potential by the different reactions of oxygen functional groups in the supercapacitor during the cycle charge and discharge process, which leads to RH. The cyclic stability of the C as a supercapacitor in the two electrolytes is changed. In the KOH electrolyte, the electrostatic repulsion and the space hindrance effect produced by the hydrolysis of the carboxyl and lactone groups make the positive pole capacitance decrease, cause the increase of the positive pole potential and the positive pole oxidation, and lead to the decay of the cycle life. In the H2SO4 electrolyte, The reversible oxidation reduction reaction of the oxygen functional group does not cause the positive shift of the positive electrode potential. Based on the study of the decay process of the RHC in the KOH electrolyte solution, the oxygen functional groups on the RHC surface are removed by heat treatment, which makes the cycle stability greatly improved. The capacity retention of the 10000 constant current charge discharge is 28.3% before the heat treatment. Up to 94.7%, but the specific capacitance of the material is reduced by 30% after heat treatment; the mass ratio of the positive and negative pole increases the positive shift of the positive pole potential, and improves the cyclic stability of RHC in KOH. When the positive and negative mass ratio is increased from the original 1:1 to the 2:1, the capacity holding rate of the 10000 constant current charge discharge is raised from the initial 28.3% to 95.3%, and the capacitance is reduced. 12%. improves the cycle stability of RHC in KOH by improving the ratio of positive and negative mass ratio, which is simpler and easier to implement than heat treatment.
(4) based on the preparation of rice husk based capacitance carbon, two green preparation processes were put forward. In the preparation process of high specific capacitance rice husk based activated carbon, the waste liquid produced in the process of RHC preparation was obtained after acidification and electrolysis, and the nano SiO2 was obtained, and the activating agent KOH and water could be used in the circulation. Compared with the common preparation process, the cost was low. In the green preparation process of the multi-stage channel active carbon in the rice husk base, the waste liquid produced in the process of RHHAC preparation is converted into activator KOH by using lime milk to realize the recycling of activator KOH and water.
【學位授予單位】：吉林大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：TQ127.11;TM53
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本文編號：2152363
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