直接硼氢化物燃料电池(DBFC)阳极催化剂的研究进展

直接硼氢化物燃料电池(DBFC)具有理论电池电压高和能量密度大等特点, 而其阳极催化剂是决定电池性能的关键因素之一。因此, 研究者们在提高阳极催化剂催化活性和降低催化剂成本方面开展了大量的研究工作。本文在简要介绍DBFC工作原理和阳极反应机理的基础上, 从催化剂种类和性能角度综述了近年来DBFC中贵金属、过渡金属以及储氢合金阳极催化剂的主要研究进展, 指出了阳极催化剂研究所面临的问题, 同时提出了今后的发展方向。     

Construction and performance evaluation of mediator-less microbial fuel cell using carbon nanotubes as an anode material

A microbial fuel cell (MFC) is a device that converts chemical energy to electrical energy using the catalytic reaction of microorganisms. We investigated the performance of mediator-less MFC with carbon nanotubes (CNTs)/graphite felt composite electrodes. The addition of CNTs to a graphite felt electrode increases the specific surface area of the electrode and enhances the charge transfer capability so as to cause considerable improvement of the electrochemical activity for the anode reaction in a MFC. The performance of the MFC using CNTs/graphite felt electrode has been compared against a plain graphite felt electrode based MFC. A CNTs/graphite felt electrode showed as high as 15% increase in the power density (252 mW/m2) compared to graphite felt electrode (214 mW/m2). The CNTs/graphite felt anode therefore offers good prospects for application in MFCs.     

高性能自支撑CuS/SnS2锂电池负极材料

过渡金属硫化物作为锂电池负极材料具有极高比容量,但其制备的电极普遍存在导电性差、体积变化大等问题,本研究设计了一种新型的自支撑CuS/SnS₂镂空片状锂电池负极材料,以导电碳布作为基底,生长包覆CuS/SnS₂镂空纳米片,具备特殊的纳米包覆结构及双金属协同效应,使其在保持较高比容量的同时具备良好的循环稳定性,整体电化学性能优异。研究不同Cu/Sn含量对CuS/SnS₂负极材料电化学性能的影响,最佳配比的CuS/SnS₂负极材料在0.2 A·g?1电流密度下循环50次后比容量为1480 mAh·g?1,库伦效率稳定在99.5%,在2 A·g?1电流密度下循环200次后比容量仍能保持在697 mAh·g?1,库伦效率为99.8%。      

金属铋纳米颗粒原位修饰碳纳米管促进锂均匀沉积

锂金属具有高理论比容量和低电化学电位,是发展高能量密度电池最有吸引力的负极材料之一。然而,锂金属负极在反复的沉积/剥离过程中,不可避免地会出现不规则的锂枝晶生长,这将严重影响锂金属电池的循环寿命和使用安全性。本研究发展了一种简单温和的策略,在碳纳米管上原位修饰铋纳米颗粒,并涂覆在商业铜箔表面用作锂金属负极的集流体。研究表明,原位修饰的铋纳米颗粒可显著促进锂均匀沉积,抑制锂枝晶生长,从而提高锂金属电池的电化学性能。在电流密度为1 mA·cm^–2的条件下,基于Bi@CNT/Cu集流体的锂铜电池循环300圈后库仑效率可稳定在98%。基于Li@Bi@CNT/Cu负极的对称电池可稳定循环1000 h。基于Bi@CNT/Cu集流体的磷酸铁锂(LFP)全电池也获得了优异的电化学性能,在1C(170m A·g^–1)倍率下可稳定循环700圈。本研究为抑制锂金属负极枝晶生长提供了新的思路。     

锂离子电池硅/碳纳米管/石墨烯自支撑负极材料研究

通过真空驱动自组装法及蒸汽处理得到结构疏松的硅/碳纳米管/石墨烯自支撑负极材料(Si/CNTs/GP)。纳米硅颗粒(50 nm)为活性物质, 均匀分布在石墨烯片层结构中间; 石墨烯作为碳基体, 通过自组装构筑形成二维导电网络; 碳纳米管(CNTs)具有超高导电性和良好的力学强度, 它通过吸附作用均匀分布在石墨烯基体上形成导电的支撑网络结构。经过蒸汽处理后, 石墨烯层间距明显增大, 层与层之间不再是紧密堆叠的结构, 而是形成一种疏松、褶皱、内部空隙丰富的片层结构。Si/CNTs/GP负极材料中丰富的内部空穴和贯穿孔洞, 提供了材料很高的比表面积, 能有效提高电解液对材料的浸润性, 极大缩短了离子传输距离。同时这些内部空穴也有效缓冲硅充放电时的体积膨胀, 提高了材料的结构稳定性和电化学性能。该负极材料在4 A/g的大电流密度下容量维持在600 mAh/g, 表现出良好的大电流循环稳定性能。     

Regulating Lithium Nucleation via CNTs Modifying Carbon Cloth Film for Stable Li Metal Anode

Li metal is demonstrated as one of the most promising anode materials for high energy density batteries. However, uncontrollable Li dendrite growth and repeated growth of solid electrolyte interface during the charge/discharge process lead to safety issues and capacity decay, preventing its practical application. To address these issues, an effective strategy is to realize uniform Li nucleation. Here, a stable lithium–scaffold composite electrode (CC/CNT@Li) is designed by melting of lithium metal into 3D interconnected lithiophilic carbon nanotube (CNT) on a porous carbon cloth (CC). The 3D interconnected CNTs successfully change the lithiophobic CC into lithiophilic nature, reducing the polarization of the electrode, ensuring homogenous Li nucleation and continuous smooth Li plating. The CNTs on the surface of CC provide adequate Li nucleation sites and reduce the areal current density to avoid Li dendrite growth. The 3D porous structure of CC/CNT offers enough free room for buffering the huge volume change during Li plating/stripping. The CC/CNT@Li composite anode exhibits dendrite‐free morphology and superior cycling performances over 500 h with low voltage hysteresis of 18, 23, and 71 mV at the current density of 1, 2, and 5 mA cm^?2, respectively.     

纳米管协同碳纳米管导电纸对石墨负极性能的影响

以碳纳米管(Multi-walled carbon nanotubes)为导电剂,协同以碳纳米管和纸纤维复合成的CNTs导电纸为集流体,对石墨负极进行电化学改性。石墨化处理碳纳米管作为负极的添加相,采用XRD、SEM和TGA对其分析。结果表明,对比单纯的石墨/铜箔负极,掺杂0.8%(质量分数)石墨化碳纳米管的石墨/铜箔负极,电池比容量由304mAh/g变为308mAh/g,相差不大,但循环效率由86%升至92%;使用CNTs导电纸做集流体时,掺杂0.8%(质量分数)石墨化碳纳米管的石墨/CNTs导电纸负极,比容量由308mAh/g升至401mAh/g,提高30%,循环效率由92%升至95%,提高3%。说明碳纳米管协同CNTs导电纸对石墨负极具有积极的改性意义。     

利用UV曝光技术研制单根定向碳纳米管阵列冷阴极

通过普通的紫外(UV)光刻工艺,结合"变倾角缩口"新技术,研制了不同发射单元尺寸的碳纳米管(CNTs)阵列阴极。扫瞄电镜分析表明,随着缩口尺寸的依次减小(从0.6μm到0.4μm,最后到0.2μm),发射单元内CNTs的根数也不断减少。当孔径缩至0.2μm时,发射单元仅由1根~3根CNTs组成,并且大部分单元顶端均有单根CNT伸出,使得整个发射体近似于单根CNT。场发射特性测试结果表明,0.2μm发射单元尺寸的阵列阴极,开启电场约2V.μm-1;当场强为20V.μm-1时,该阵列的电流密度达到0.35A.cm-2,比1μm尺寸的阵列阴极提高了近4倍,比连续生长的薄膜CNTs阴极则高1~2个数量级。     

催化裂解天然气于碳毡内低成本合成碳纳米管

基于制备碳/碳(C/C)复合材料的等温化学气相渗透(ICVI)技术,在1010～1100℃用Fe催化裂解工业天然气可在碳毡内原位合成出碳纳米管(CNTs).扫描电镜(SEM)观察结果表明,1060℃合成的CNTs具有较好的覆盖形貌和均匀管径(110～120nm)且纯净度高.高分辨率透射电镜(HRTEM)和Raman光谱测试结果进一步表明,该温度下合成的CNTs结晶度高,与碳纤维间结合力强.     

四氧化三钴/碳纳米管薄膜的水热合成及其储锂性能

以5-磺基水杨酸和戊二酸为螯合和氧化试剂,在水热条件下将硫酸钴氧化成纳米级Co₃O₄。以碳纳米管薄膜为载体将Co₃O₄颗粒紧密地附着在碳纳米管上使其填充入碳纳米管薄膜的空隙生成Co₃O₄/碳纳米管复合材料薄膜(Co₃O₄@CNTs),并研究其储锂性能。电化学测试结果表明,Co₃O₄@CNTs薄膜具有较高的放电比容量和优异的倍率性能,在0.2C倍率下初始放电比容量高达1712.5 mAh·g^-1,100圈循环后放电比容量为1128.9 mAh·g^-1的;在1C倍率下100圈循环后放电比容量仍然保持527.8 mAh·g^-1。Co₃O₄@CNTs薄膜优异的性能源于Co₃O₄与CNTs的协同作用。高分散性的Co₃O₄增大了活性材料与电解液之间的接触面积,CNTs有助于形成良好的导电网络提高电子电导率,进而提高了Co₃O₄负极材料的循环性能和倍率性能。     

竹基碳纤维/MoS2锂离子电池负极材料

随着电子产品、电动汽车以及智能电网的快速发展,不仅需要锂离子电池(LIBs)具有优异的储锂性能,而且要求电极材料成本低廉、资源丰富和绿色环保。基于碳负极材料的优点,将废弃的一次性竹筷,在碱性溶液中经过可控的热处理,利用竹子中丰富的天然纤维素,从而获得尺寸均匀的碳纤维(CFs)材料。相比于石墨电极,竹基CFs作为LIBs的负极材料时表现出优异的电化学性能。为进一步提高其储锂性能,以CFs为骨架,通过水热法在其表面制备了一层二硫化钼(MoS₂)纳米花,形成核壳结构的CFs/MoS₂复合电极材料。电化学测试结果表明,CFs电极在200 mA/g的电流密度下循环500次,放电比容量仍有381.1 mA·h/g;CFs/MoS₂复合材料在1000 mA/g的大电流密度下经过1000次循环,仍保持有843 mA·h/g的放电比容量。      

SnO2 nanoparticles distributed on multi-walled carbon nanotubes and ball-milled graphite as anode materials of lithium ion batteries

SnO2 nanoparticles were supported on ball-milled graphite (BMG) or carbon nanotubes (CNTs) using a chemical reduction method with ethylene glycol, and the electrochemical properties of the nanocomposites were evaluated as anode active materials of lithium-ion batteries. The BMG and CNTs contributed to an increase in both the capacity enhancement and cyclic stability compared to that of commercial graphite. In particular, the mixture electrode of SnO2/BMG:SnO2/CNT = 3:1 (in weight ratio) showed higher performance in the reversible capacity and cyclic stability than did the SnO2/BMG and SnO2/CNT electrodes. This might be resulted from the network formation for excellent electronic path by CNT distributed on SnO2/BMG composites.     

碳纳米管与石墨烯协同改性天然石墨及其电化学性能

以碳纳米管和氧化石墨烯为原料,二者按5∶3混合超声分散再高温还原制备碳纳米管/石墨烯/天然石墨(CNTs/rGO/NG)锂离子复合负极材料。采用扫描电镜(SEM)、X射线衍射(XRD)、红外光谱(FTIR)和电化学测试等分析技术对复合材料的形貌、结构、电化学进行表征。结果表明:石墨烯和碳纳米管在天然石墨表面形成三维立体网络结构。与纯天然石墨相比,CNTs/rGO/NG复合材料具有良好的倍率性能和循环寿命,在0.1C时首次放电比容量为479mAh/g,可逆容量达473mAh/g,循环100次后容量为439.5mAh/g,容量保持率为92%,在0.5,1,5C不同电流倍率时容量依次为457,433,394mAh/g。     

质子交换膜燃料电池中碳纳米管负载的氧电极材料制备与表征

本文介绍了碳纳米管(CNTs)在质子交换膜燃料电池催化剂中的应用,对Pt/CNTs及Pt/C催化剂的比表面积、孔径、孔分布及金属表面分散情况进行了比较.实验发现,具备典型中孔结构的CNTs使得铂金属在其表面分散更加均匀.在催化剂制备工艺的研究中发现,合适的硝酸(40%)处理会使催化剂载体具备更加适宜的孔结构.通过本文的讨论,可以认为Pt/CNTs是一种可以应用在质子交换膜燃料电池上很有前景的电催化剂.     

Amorphous Sn modified nitrogen-doped porous carbon nanosheets with rapid capacitive mechanism for high-capacity and fast-charging lithium-ion batteries

Sn-based materials are considered as a kind of potential anode materials for lithium-ion batteries (LIBs) owing to their high theoretical capacity. However, their use is limited by large volume expansion deriving from the lithiation/delithiation process. In this work, amorphous Sn modified nitrogen-doped porous carbon nanosheets (ASn-NPCNs) are obtained. The synergistic effect of amorphous Sn and high edge-nitrogen-doped level porous carbon nanosheets provides ASn-NPCNs with multiple advantages containing abundant defect sites, high specific surface area (214.9 m²·g⁻¹), and rich hierarchical pores, which can promote the lithium-ion storage. Serving as the LIB anode, the as-prepared ASn-NPCNs-750 electrode exhibits an ultrahigh capacity of 1643 mAh·g⁻¹ at 0.1 A·g⁻¹, ultrafast rate performance of 490 mAh·g⁻¹ at 10 A·g⁻¹, and superior long-term cycling performance of 988 mAh·g⁻¹ at 1 A·g⁻¹ after 2000 cycles with a capacity retention of 98.9%. Furthermore, the in-depth electrochemical kinetic test confirms that the ultrahigh-capacity and fast-charging performance of the ASn-NPCNs-750 electrode is ascribed to the rapid capacitive mechanism. These impressive results indicate that ASn-NPCNs-750 can be a potential anode material for high-capacity and fast-charging LIBs.     

A novel hierarchically carbon foam templated carbon nanotubes/polyaniline electrode for efficient electrochemical supercapacitor

In this work, a high-performance electrode material has been fabricated by the incorporation of carbon nanotubes (CNTs) and polyaniline (PANI) on a carbon foams (CF) to improve its electrochemical performance. The microstructure and performance of as-prepared material was characterized in detail. Results showed that the resultant material exhibited a high gravimetric capacitance up to 467.1?F g^?1, higher energy density of 104. 2?Wh kg^?1 and power density of 3000?W kg^?1 at a current density 3?A g^?1 when the electrochemical doping time of PANI equals to 20?min. Furthermore, it appeared a good cycling stability with capacitance retention of 94.5% after 10000 cycles. The enhanced electrochemical performance can be attributed to the unique carbon nanostructure and synergistic effects of active materials CNTs and PANI. It indicates that this novel CF/CNTs/PANI-20 composite is a promising candidate for electrochemical capacitors.     

Effect of catalyst thickness and plasma pretreatment on the growth of carbon nanotubes and their field emission properties

We demonstrated that the diameter and the density of carbon nanotubes (CNTs) which had a close relation to electric-field-screening effect could be easily changed by the control of catalytic Ni thickness combined with NH3 plasma pretreatment. Since the diameter and the density of CNTs had a tremendous impact on the field-emission characteristics, optimized thickness of catalyst and application of plasma pretreatment greatly improved the emission efficiency of CNTs. In the field emission test using diode-type configuration, well-dispersed thinner CNTs exhibited lower turn-on voltage and higher field enhancement factor than the densely-packed CNTs. A CNT film grown using a plasma-pretreated 25 angstroms-thick Ni catalyst showed excellent field emission characteristics with a very low turn-on field of 1.1 V/microm @ 10 microA/cm2 and a high emission current density of 1.9 mA/cm2 @ 4.0 V/microm, respectively.     

In situ preparation and mechanical properties of CNTs/MCMBs composites

By adding carbon nanotubes (CNTs) into medium temperature coal tar pitch, mesocarbon microbeads (MCMBs) were obtained via thermal condensation, then CNTs/MCMBs composites were in situ prepared using compression molding. The morphology, structure and mechanical properties of CNTs/MCMBs composites were characterized by optical microscope, digital camera, scanning electron microscope (SEM) and mechanical test machine. Results showed that CNTs were used as the nucleating agent and could inhibit the growth and coalescence of MCMBs. The optical textures of CNTs/MCMBs composites showed similar characteristics to the thermal condensation products from coal tar pitch with CNTs. The mass ratio of CNTs to coal tar pitch played an important role in the mechanical properties of CNTs/MCMBs composites. The density and bending strength of CNTs/MCMBs composite first increased and then decreased with the increase of the proportion of CNTs. When the proportion of CNTs was 5 wt%, the density of the composite reached the maximum (1.76 g/cm³). In addition, the bending strength of the composite reached the maximum (79.6 MPa) as adding 2 wt% CNTs into coal tar pitch.     

锂离子电池碳纳米管负极材料储锂性能研究

将碳纳米管用于锂离子电池负极材料,用循环伏安及充放电实验研究了电极的性能.结果表明,碳纳米管用作锂离子电池负极,具有较高的储锂容量,首次放电容量达560mAh/g,但首次不可逆容量损失也大,高达430mAh/g.经过第1次充放电的容量损失后,随后各次的容量损失很小,碳纳米管的循环性能趋于稳定.     

TiO2/C复合材料用于钠离子电池负极的性能研究

近年来,TiO₂作为钠离子电池(NIB)负极材料,因其低成本和高稳定性等优势受到广泛关注。但受TiO₂本征电子导电性的固有限制,使得TiO₂作为NIB负极材料导电性较差,导致其容量和倍率等性能不理想。利用海藻酸钠与金属离子自主交联反应的特性,将反应产物在最佳温度下进行简单碳化,制备了具有分级多孔结构的TiO₂/C复合材料,其中TiO₂纳米颗粒均匀地分布在多孔互连的碳基体中,该结构提升了复合材料导电性的同时扩展了钠离子反应的附着位点。将TiO₂/C复合材料用于NIB负极材料,在100 mA·g^-1的电流密度下循环300圈后,电池可逆比容量维持在180.4 mAh·g^-1;进一步,在更高的1000 mA·g^-1电流密度下经过1000次循环后,电池可逆比容量维持在102.3 mAh·g^-1,充分显示出TiO₂/C复合材料作为NIB负极材料的应用潜能。