马尾藻基超级活性炭的电化学性能研究

选取马尾藻作为前驱体制备超级电容器电极材料,使用氢氧化钾活化法,探究活化温度、活化时间、浸渍比对电化学性能的影响。其中SAC-800-120-4的比表面积可超过2 400 m²/g,介孔率为56%。采用二电极测试装置,以6 mol/L的KOH溶液作为电解液,在1 A/g的电流密度下,SAC-800-120-4的质量比电容达到了290 F/g,在5 A/g的电流密度下质量比电容为257 F/g,电容保持率为89%,具有优良的倍率性能。在1 A/g的电流密度下,SAC-800-120-4的能量密度为36.62 W∙h/kg,功率密度为604.78 W/kg。     

Study on preparation and electrochemical properties of biomass-derived spherical activated carbon

以生物质风化煤系腐殖酸（LHA）为炭质前驱体,通过溶剂蒸发和KOH活化方法制备了球形活性炭。使用扫描电子显微镜（SEM）、N2物理吸脱附仪等手段对球形活性炭形貌和孔道结构进行了表征;还将活性炭组装成扣式电容器,进行了充放电容量、循环伏安特性和交流阻抗行为等电化学性能测试。结果表明：所制备的球形活性炭具有良好的球形度,通过少量碱活化后球形活性炭BET表面积为2034 m2/g、总孔容为1.24 cm3/g、平均孔径为2.38 nm。同时,以球形活性炭作为电极材料应用于水系超级电容器后显示了优异的电化学性能,比电容可达到319 F/g,在进行10000次充放电后,比电容保持率为98.9%。此外,球形活性炭相比于颗粒活性炭具有更好的导电性,也展现了更加优异的倍率性能和循环性能。因此说明LHA基球形活性炭是一种有潜在优势的超级电容器材料。     

Fabrication of microporous and mesoporous carbon spheres for high‐performance supercapacitor electrode materials

Microporous and mesoporous carbon spheres (CSs) were fabricated using resorcinol and formaldehyde as precursors in the presence of Pluronic F127 as porogen and KOH as the active agent. The textural characteristic and morphology were characterized by scanning electron microscopy, transmission electron microscopy, and N₂ adsorption/desorption techniques. Pluronic F127 played an important role for generating mesopores, while KOH activation brought abundant micropores and resulted in a combined microporous and mesoporous structure of the CSs. The results showed that a typical sample (denoted as CS‐F‐K) possessed a spherical shape, with a high specific surface area of 735.4 m²/g, large pore volume of 0.622 cm³/g, and combined microporous and mesoporous structure, which endowed CS‐F‐K good electrochemical performance with a specific capacitance of 182 F/g under a current density of 0.5 A/g, remarkable rate performance, and long‐term cycling stability. After 1000 cycles at 3 A/g, CS‐F‐K electrode can still remain the specific capacitance of 154.8 F/g with a retention of 98.9%. The excellent electrochemical performance of CS‐F‐K was mainly attributed to the micro‐mesoporous structure, which promoted the ion accumulation on the electrode surface and facilitated fast ion transportation. Copyright © 2015 John Wiley & Sons, Ltd.     

Nitrogen-doping activated biomass carbon from tea seed shell for CO2 capture and supercapacitor

Activated carbon is a promising material that has a broad application prospect. In this work, biomass (tea seed shell) was used to prepare activated carbon with KOH activation (referred to as AC), and nitrogen was doped in activated carbon using melamine as the nitrogen source (referred to as NAC-x, where x is the mass ratio of melamine and activated carbon). The obtained activated biomass carbon (activated bio-carbon) samples were characterized by Brunauer–Emmett–Teller (BET)-specific surface area analysis, ultimate analysis, X-ray photoelectron spectroscopy (XPS) analysis, Raman spectrum analysis, and X-ray diffraction (XRD) patterns. The specific surface areas of activated bio-carbons were 1503.20 m²/g (AC), 1064.54 m²/g (NAC-1), 1187.93 m²/g (NAC-2), 1055.32 m²/g (NAC-3), and 706.22 m²/g (NAC-4), revealing that nitrogen-doping process leads to decrease in specific surface area. XPS analysis revealed that the main nitrogen-containing functional groups were pyrrolic-N and pyridinic-N. The capacity of CO₂ capture and electrochemical performance of activated bio-carbon samples were investigated. The CO₂ capturing capacity followed this order: AC (3.15 mmol/g) > NAC-2 (2.75 mmol/g) > NAC-1 (2.69 mmol/g) > NAC-3 (2.44 mmol/g) > NAC-4 (1.95 mmol/g) at 298 K at 1 bar, which is consistent with the order of specific surface area. The specific surface area played a dominant role in CO₂ capturing capacity. As for supercapacitor, AC-4 showed the highest specific capacitance (168 F/g) at the current density of 0.5 A/g, but NAC-2 showed the best electrochemical performance (89 F/g) at 2 A/g. Nitrogen-containing functional groups and specific surface area both had an important impact on electrochemical performance. In general, NAC-3 and NAC-2 produced excellent electrochemical performance. Compared with NAC-3, less melamine was used to prepare NAC-2; therefore, NAC-2 was considered as the best activated bio-carbon for supercapacitor for 141 F/g (at 0.5 A/g), 108 F/g (at 1 A/g), and 89 F/g (at 2 A/g) in this work.     

Porous bamboo-like CNTs prepared by a simple and low-cost steam activation for supercapacitors

How to prepare porous carbons with appropriate structure for supercapacitors is a big challenge. In general, activation is the simplest way to obtain porous carbons. Porous bamboo-like CNTs were fabricated by simple activating sulfonated polymer nanotubes with steam at 800°C. Compared with the un-activated one, activated carbon nanotubes (ACNTs) have good tubular structure, larger specific surface area and rich porosity thanks to the protection of steam during the activation. The ACNTs electrode for supercapacitors displays a specific capacity of 276 F g⁻¹ at 1 A g⁻¹. When assembling ACNTs into a symmetrical supercapacitor, the specific capacity of the device can retain 98% after 10 000 cycles, and this result shows the great application prospect of ACNTs for supercapacitors.     

Recent progress in the application of carbon materials to supercapacitors and lead-carbon batteries

新型炭材料是电化学储能领域中非常重要的一类储能材料,目前广泛应用于各种电化学储能器件.本文综述了具有电容特性的高比表面积炭材料在超级电容器与铅炭电池中的应用.采用不同的方法合成具有高比表面积的新型炭材料作为超级电容器电极材料,能够得到较高的比容量.适量高比表面积的炭材料应用于铅酸电池负极,形成铅炭电池,极大地提高了电池的储能特性.论文最后探讨了新型炭材料在超电容以及铅炭电池中应用的发展方向.     

Hierarchically porous carbon from biomass tar as sustainable electrode material for high-performance supercapacitors

The byproduct tar from biomass gasification process had seriously impeded development and applications of this technology, thus novel path for biomass tar valorization is had been continuously pursued. Given its high carbon content, this work attempted to convert biomass tar into hierarchically porous carbon by thermal activation with acetate potassium. The optimal product produced with mass ratio of biomass tar to acetate potassium of 1:3 and activation temperature at 800 °C was revealed as excellent electrode material for high-performance supercapacitor, which demonstrated electrochemical capacitance up to 310.4 F/g at 0.2 A/g, whilst preserved 91% of initial capacitance after 5000 charge-discharge circles at current density of 5 A/g. These excellent properties had arisen from the open and hierarchical porosity and large surface area. This work disclosed the great potential of biomass tar as sustainable and competent candidate for fabricating high-performance electrode material for electrochemical energy devices, and may bring up new opportunities to development of biomass gasification technologies.     

Synthesis of biomass porous carbon materials from bean sprouts for hydrogen evolution reaction electrocatalysis and supercapacitor electrode

Biomass carbon porous materials have attracted more attention for their green, renewable and simple preparation process. They have a large specific surface area and abundant pore structure. Their structural characteristics make them expose more active sites and allow the electrolyte ions to transfer quickly, which indicates they have great application prospects in hydrogen evolution reaction (HER) and supercapacitors. In the present work, bean sprout (BS) was used as the carbon source because of its nitrogen self-doped characteristic and advantages of low-cost, simple, mature production process. The high temperature carbonization method without physical and/or chemical activation was used to synthesize the carbon materials. And different pyrolysis temperature (500–900 °C) was investigated in this work. The as-prepared BS-800 were used as the bifunctional electrode materials. The measurement results showed that BS-800 exhibited the high activity for HER and high specific capacitance for supercapacitors.     

Microstructure regulation of super activated carbon from biomass source corncob with enhanced hydrogen uptake

A series of super activated carbon have been prepared by potassium hydroxide activation of corncob. The as-obtained samples were characterized by SEM, TEM and N₂-sorption. The results show morphologies and textural of activated carbon are highly depended on the activation temperature, heating rate, whereas the activation time is not a key factor. Morphologies and porous structure of activated carbons can be regulated by adjusting preparation parameters. A super activated carbon with BET surface area of 3530 m²/g and total pore volume of 1.94 cm³/g is obtained. However, the other activated carbon with smaller pore size exhibited the highest hydrogen uptake capacities exceeding 2.85 wt% at −196 °C and 1.0 bar, whose BET surface area is only 2988 m²/g. The correlation investigations show the micropore volume between 0.65 nm and 1.5 nm can be more important than BET surface area and total pore volume for hydrogen uptakes at −196 °C. The present results indicate that the corncob-derived activated carbons can be promising materials for hydrogen storage.     

A synthesis method for cobalt doped carbon aerogels with high surface area and their hydrogen storage properties

Carbon aerogels doped with nanoscaled Co particles were prepared by first coating activated carbon aerogels using a wet-thin layer coating process. The resulting metal-doped carbon aerogels had a higher surface area (∼1667 m² g⁻¹) and larger micropore volume (∼0.6 cm³ g⁻¹) than metal-doped carbon aerogels synthesised using other methods suggesting their usefulness in catalytic applications. The hydrogen adsorption behaviour of cobalt doped carbon aerogel was evaluated, displaying a high ∼4.38 wt.% H₂ uptake under 4.6 MPa at −196 °C. The hydrogen uptake capacity with respect to unit surface area was greater than for pure carbon aerogel and resulted in ∼1.3 H₂ (wt. %) per 500 m² g⁻¹. However, the total hydrogen uptake was slightly reduced as compared to pure carbon aerogel due to a small reduction in surface area associated with cobalt doping. The improved adsorption per unit surface area suggests that there is a stronger interaction between the hydrogen molecules and the cobalt doped carbon aerogel than for pure carbon aerogel.     

Button cell supercapacitors with monolithic carbon aerogels

Carbon aerogels are highly porous materials prepared via pyrolysis of resorcinol–formaldehyde aerogels. The density of the aerogels can be varied in a wide range, whereby the major part of the pores is accessible to ionic conductors. Therefore, the application of high surface area aerogels as electrodes in supercapacitor devices is promising. In the present publication, the integration of thin monolithic aerogel composites in button cell casings is presented. The preparation of thin and mechanically stable aerogel electrodes was performed via integration of carbon fibers into the aerogel skeleton. In order to increase the external electrode area in the button cells (volume: 2.1 cm³) a special folding technique for the electrodes (thickness: 180 μm) was employed. The aerogel capacitors exhibit an excellent long term stability with no significant degradation after 80,000 charging and discharging cycles. According to a ragone-evaluation of the impedance data, the maximum power output and energy content for the aerogel button cells are 4.6 W and 4.9 mWh, respectively. The influence of CO₂-activation on the capacitive and resistive behavior of the electrodes in different aqueous electrolytes is analyzed using innovative analytical methods for cyclic voltammetry and impedance spectroscopy.     

Synthesis of polypyrrole (PPy) based porous N-doped carbon nanotubes (N-CNTs) as catalyst support for PEM fuel cells

In this study, it was aimed to synthesize catalytically active, high surface area carbon nanotubes (CNTs) by means of nitrogen doping (N-doping). The synthesized nitrogen doped carbon nanotubes (N-CNTs) were used as Pt catalyst support in order to improve oxygen reduction reaction (ORR) kinetics at the cathode electrode in PEM fuel cell. Polypyrrole (PPy) was served as both carbon and nitrogen source and FeCl₃ solution was used as oxidizing agent in the synthesis procedure of N-CNTs. Chemical activation of the materials was made with potassium hydroxide (KOH) solution during 12 and 18 h time periods. It was considered that activation period is of great importance on the properties of the synthesized PPy based N-CNTs. 12 h activated N-CNTs gave higher surface area (1607.2 m²/g) and smaller micropore volume (0.355 cm³/g) in comparison to 18 h activated N-CNTs having smaller surface area (1170.7 m²/g) and higher micropore volume (0.383 cm³/g). PEM fuel cell performance results showed that 12 h activated N-CNTs are better catalyst supports than 18 h activated N-CNTs for Pt nanoparticle decoration.     

High hydrogen storage capacity of rice hull based porous carbon

A kind of porous carbon with high specific surface area (approximately 4000 m²/g) was prepared from rice hull through carbonization and sodium hydroxide activation. The effects of preparation parameters on the characteristics of the porous carbon were studied. The properties of these porous carbon samples were investigated by X-ray diffraction and scanning electron microscope (SEM) and Fourier transform infrared spectroscopy. The rice hull based porous carbon exhibits high hydrogen storage capacity of 7.7 wt% at 77 K and 1.2 MPa.     

Characterizing capacity loss of lithium oxygen batteries by impedance spectroscopy

Polymer based carbon aerogels were prepared by synthesis of a resorcinol formaldehyde gel followed by pyrolysis at 1073 K under Ar and activation of the resultant carbon under CO₂ at different temperatures. The prepared carbon aerogels were used as active materials in the preparation of cathode electrodes for lithium oxygen cells and the electrochemical performance of the cells was evaluated by galvanostatic charge/discharge cycling and electrochemical impedance measurements. It was shown that the storage capacity and discharge voltage of a Li/O₂ cell strongly depend on the porous structure of the carbon used in cathode. EIS results also showed that the shape and value of the resistance in the impedance spectrum of a Li/O₂ cell are strongly affected by the porosity of carbon used in the cathode. Porosity changes due to the build up of discharge products hinder the oxygen and lithium ion transfer into the electrode, resulting in a gradual increase in the cell impedance with cycling. The discharge capacity and cycle life of the battery decrease significantly as its internal resistance increases with charge/discharge cycling.     

Nickel silicate hydroxide on hierarchically porous carbon derived from rice husks as high-performance electrode material for supercapacitors

Nickel silicate hydroxide on hierarchically porous carbon derived from rice husks is prepared as electrode material for supercapacitors. AAEMs¹ in rice husks and CO₂ promote the development of pores, which act as pore-forming agent and catalyst respectively. The rice husks carbon is used as the substrate and the SiO₂ in rice husks is converted into Ni–Si compound by loading Ni. The C/NiSi-600-1 shows remarkable electrochemical performance with 237.07 F/g at 0.5 A/g. The performance declines with crystalline SiO₂ formed above 900 °C. A high-performance asymmetric water-system supercapacitor device is fabricated by C/NiSi-600-1 and activated carbon. This device shows capacitance of 142 mF/cm² at 4 mA/cm², the energy density of 25.24 Wh/kg at 551.4 W/kg and great cycle stability with 90% after 10,000 cycles. This work provides new insights into the green application of rice husks and promotes the development of electrode materials for supercapacitors.     

生物质活性炭的制备及其在阳极中的性能

以竹子为原料制备生物质活性炭,使用HNO3溶液浸渍实现活性炭表面改性和降低灰分,在流化床电极直接碳燃料电池阳极半电池中考察活性炭的极化性能。结果表明:活化温度为1173K、活化时间为2h、碱炭比为1时,活性炭比表面积为1264m2/g,电阻率为1569μΩ.m;HNO3溶液浸渍后,活性炭表面含氧官能团的种类和含量明显增加,灰分也有较大程度降低,最佳HNO3浸渍浓度为2mol/L;自制活性炭在半电池中的极化性能明显优于石墨和活性炭纤维。     

Fe(NO_3)_3活化制备棉经纬纶废料介孔炭及其吸附Cr(VI)研究

以棉经纬纶废料为原料,利用Fe(NO3)3为活化剂制备介孔炭。通过单因素实验考察Fe(NO_3)_3和棉经纬纶废料质量比、活化温度和活化时间对介孔炭碘值和得率的影响,得出其最佳制备工艺条件为:质量比为0.5∶1、活化温度为700°C、活化时间为0.5 h,制得的介孔炭碘值和得率分别为409.78 mg·g~(-1)和13.72%,比表面积为382.95 m~2·g~(-1),介孔比表面积和介孔容积分别为335.16 m~2·g~(-1)和0.79 cm~3·g~(-1)。介孔炭对Cr(VI)的吸附量随pH增加而减小,最大吸附量为46.03 mg·g~(-1),吸附行为符合Langmuir模型,为单分子层吸附。     

Green and facile synthesis of porous carbon spheres from waste solution for high performance all-solid-state symmetric supercapacitors

Porous carbon spheres materials display huge potential for energy storage, but their general synthesis need chemical activation agent with highly corrosive to create pores. In this work, a simple, environment-friendly and less time-demanding method is used to prepared porous carbon spheres using K₂FeO₄ as activation agent and waste solution as the precursor. The K₂FeO₄ employ in this work acts both as an activating agent and a catalyst. In addition, replacing KOH with K₂FeO₄ does not only reduce the corrosion of equipment but also increases the content of oxygen. The optimized porous carbon spheres with high specific surface area, hierarchical pore structure and surface heteroatom can deliver a high specific capacitance of 260 F g⁻¹ at 0.1 A g⁻¹ and good cycling stability (90% retention after 15000 cycles at 5 A g⁻¹). Furthermore, the all-solid-state symmetric supercapacitors fabricated based on as-prepared samples exhibit good electrochemical performance in the PVA/KOH electrolyte. This work offers a green route to convert waste solution into porous carbon spheres, which are promising candidate material for supercapacitors to energy storage.     

Sol-gel derived mixed phase (Mn,Ti)-oxides/graphene nanoplatelets for hybrid supercapacitors

In this investigation, (Mn, Ti)- oxides were prepared using pluronic 123 templating assisted sol-gel method. Sol-A with Ti precursor in ethanol was acidified with HCl whereas sol-B containing Mn precursor was prepared in ethanol containing 5 wt% pluronic 123 surfactant. Gelation was accomplished by the addition of de-ionized water. As-prepared gels were aged for 24 hours, dried at 80°C for 12 hours and calcined at 500°C to 1200°C for 5 hours to obtain powdered electrode materials, which were analyzed by x-ray diffraction, scanning electron microscopy/energy-dispersive x-ray, and Brunauer-Emmett-Teller (BET) surface area analysis. Hybrid supercapacitors were fabricated using the sol-gel derived (Mn, Ti)- oxides and Gr-nanoplatelets electrodes with aqueous KOH (potassium hydroxide) as electrolyte. Fabricated supercapacitors were charged with 2.0 V and 0.01 A for 10 minutes. Charged supercapacitors were tested via cyclic voltammetry to determine specific capacitance. For the powdered materials prepared with Mn:Ti at 65:35 wt% and calcined at 500°C, x-ray diffraction analysis revealed the presence of TiO₂-rutile, Mn₂O₃ and Mn₃O₄ as 20%, 60%, and 18%, respectively. At higher calcination temperature, TiO₂-rutile and Mn₂O₃ phases were found to be absent with the presence of higher perovskite (TiMnO₃) phase. Both pore volume and BET specific surface area was found to decrease with increase in calcination temperature. The specific capacitance was found be dependent on Mn:Ti wt% used to prepare the powdered materials as well as the calcination conditions. The gel prepared with Mn:Ti of 30:70 wt% followed by 2-step calcination yielded a maximum specific capacitance.     

活化剂种类对生物质活性炭理化特性的影响

采用KOH、K2CO3和ZnCl2为活化剂,椰壳、竹子、杨木和棉秆为原材料制备活性炭,研究不同活化剂对生物质热解活化产物及活性炭理化特性的影响.结果表明,KOH活化时,生物质的固液气三相比例均衡,CO体积产量最高,活性炭的表面官能团稳定性最好,骨架破碎,微孔结构发达,微孔面积可达749.90 m2/g.K2CO3活化时...