Hydrogen storage on nickel catalysts supported on amorphous activated carbon

We have studied the hydrogen storage at room temperature and high pressure on nickel catalysts impregnated on an amorphous commercial activated carbon. The catalysts were studied by means of the BET method, XRD, metal surface area and temperature programmed desorption. It was shown that the catalysts could store significant amounts of hydrogen at room temperature and high pressure (up to 0.53% at 30 bars against 0.1% for the activated carbon). Various factors influencing the level of hydrogen uptake were examined and discussed. The hydrogen spillover would be the driving force for the hydrogen storage. Two mechanisms of hydrogen uptake are proposed.     

Graphite nanofibers prepared from catalytic graphitization of electrospun poly(vinylidene fluoride) nanofibers and their hydrogen storage capacity

Electrospun poly(vinylidene fluoride) nanofibers were carbonized with iron(III) acetylacetonate to induce catalytic graphitization within the temperature range 800–1800 °C. Carbonization in the presence of the catalyst produced graphite nanofibers (GNFs). Their structural properties and morphology were investigated. GNFs with a high surface area of 377–473 m²/g showed the typical Type II containing mesopore in nitrogen adsorption–desorption isotherms. The hydrogen storage capacity of these GNFs was evaluated by the gravimetric method using a magnetic suspension balance (MSB) at room temperature and about 80 bar. The hydrogen storage capacity was 0.11–0.18 wt.%. The effective pore size for hydrogen storage compared to the diameter of the hydrogen molecule is discussed.     

Hydrogen diffusion in quasicrystalline and amorphous ZrCuNiAl

We report on the direct determination of the hydrogen self-diffusion constant D in the hydrogen-storage Zr_69.5Cu₁₂Ni₁₁Al_7.5 alloy, prepared in both the icosahedral quasicrystalline and the bulk metallic glass phases, using the technique of NMR diffusion in a static fringe field of a superconducting magnet. The diffusion constant exhibits strong dependence on temperature and hydrogen concentration. D was found to obey classical Arrhenius thermally activated over-barrier hopping form, whereas the significant decrease of D with increasing hydrogen-to-metal concentration ratio H/M is a result of two effects – the increase of the activation energy for hydrogen jumps between interstitial sites due to lattice expansion upon hydrogenation and the decreasing number of available empty interstitials due to site blocking and creation of defects in the lattice during hydrogen loading. The actual alloy structure – the icosahedral, approximant or metallic glass – appears to be less important for the hydrogen diffusivity.     

Nylon 66 nanofibers prepared by CO2 laser supersonic drawing

Nylon 66 nanofibers were prepared by irradiating as‐spun nylon 66 fibers with radiation from a carbon dioxide (CO₂) laser while drawing them at supersonic velocities. A supersonic jet was generated by blowing air into a vacuum chamber through the fiber injection orifice. The fiber diameter depended on the drawing conditions used, such as laser power, chamber pressure, laser irradiation point, and fiber supply speed. A nanofiber obtained at a laser power of 20 W and a chamber pressure of 20 kPa had an average diameter of 0.337 μm and a draw ratio of 291,664, and the drawing speed in the CO₂ laser supersonic drawing was 486 m s^?1. The nanofibers showed two melting peaks at about 257 and 272°C. The lower melting peak is observed at the same temperature as that of the as‐spun fiber, whereas the higher melting peak is about 15°C higher than the lower one. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 40015.     

清洁煤技术与CO_2地质封存

中国能源资源特点决定现在以煤为主的消费结构,但煤炭在消费过程中存在高污染和低效率的问题,因此为提高资源利用率,煤炭行业面临结构调整。煤炭行业的清洁化、高效化、低碳化将是产业发展方向,煤炭高效洁净转化将取代传统的转化技术,如何解决煤炭利用过程中产生的CO2是清洁煤技术面临的新问题。通过研究清洁煤技术与CO2地质封存技术,特别是深部盐水层封存技术,为煤炭利用中产生的CO2排放提供了一种大规模、安全、稳定的存储方式,从而解决目前中国能源结构造成的CO2排放问题。     

Macroporous polymer-derived SiO2/SiOC monoliths freeze-cast from polysiloxane and amorphous silica derived from rice husk

A freeze-casting route towards macroporous SiOC/SiO₂ ceramic nanocomposites from preceramic polymers was developed. Amorphous SiOC/SiO₂ monolith with pore channels aligned along the freezing direction were obtained from commercially available methyl-phenyl-vinyl-hydrogen polysiloxane (Silres® H62C) and amorphous silica derived from rice husk ash freeze-cast with water or tert-butyl alcohol, crosslinked and pyrolyzed at 1100 °C in nitrogen. The influence of processing parameters such as solvent (tert-butyl alcohol or water), polymer to silica ratio (2:1, 1:1, 1:2), cooling rate (2, 4, 6 °C/min) and pre-crosslinking of polysiloxane on the porosity and structure of the obtained ceramic nanocomposites were assessed by X-ray tomography, XRD, solid state NMR, scanning electron microscopy and mercury porosimetry. The microstructure of SiOC ceramics derived from the Silres H62C polysiloxane was studied as well.     

瑞典二氧化碳捕集与封存技术的研发现状

瑞典参与的二氧化碳捕集与封存(CCS)项目多是欧盟项目,与英国、德国、丹麦、挪威、法国等国一起开展技术研究和示范项目的建设。瑞典在二氧化碳的捕集、运输和封存等各个环节的技术和政策都有研究,捕集技术的实验平台和示范项目则多设在瑞典境外的大型火力发电厂,封存地则需要考虑运输、地质条件等因素。     

Electrospun polyimide nanofibers and their applications

Aromatic polyimides (PIs) are high-performance polymers with rigid heterocyclic imide rings and aromatic benzene rings in their macromolecular backbones. Owing to excellent mechanical properties and thermal stability, as well as readily adjustable molecular structures, PIs have been widely adopted for many applications related to electronics, aerospace, automobile, and other industries. In recent years, PI fibers prepared by electrospinning of polyamic acid (PAA) precursor nanofibers followed by imidization (commonly known as electrospun PI nanofibers) have attracted growing interests. Herein, the preparation, evaluation, and application of electrospun PI nanofibers are reviewed. PI polymers and the electrospinning technique are introduced first followed by the preparation of electrospun nanofibers of homo-PI, co-PI, blend-PI, and PI composite. Subsequently, the mechanical and thermal properties of electrospun PI nanofibers are presented; in particular, the mechanical properties of individual electrospun PI nanofibers are highlighted. Thereafter, various applications of electrospun PI nanofibers are outlined, including reinforcement of composites, Li-ion battery separators, fuel cell proton exchange membranes, sensors, microelectronics, high-temperature filtration media, super-hydrophobic PI nanofibers, and PI-based carbon nanofibers. In the final section of conclusions and perspectives, future research endeavors and high-value applications of electrospun PI nanofibers are discussed.     

Electrospun melamine-blended activated carbon nanofibers for enhanced control of indoor CO2

Electrospun carbon nanofibers were activated with melamine–polyacrylonitrile [melamine-blended carbon nanofibers (MACNFs)] for use as a fibrous adsorbent for indoor CO₂ removal. Although, melamine doping was intended solely to incorporate basic nitrogen functionalities on the nanofibers, it also shortened fabrication time, conserving time, and energy cost. The specific surface area and microporosity of the fibers were enhanced from 412 m² g⁻¹ and 0.1646 cm³ g⁻¹ to 547 m² g⁻¹ and 0.220 cm³ g⁻¹, respectively, upon final CO₂ activation of the nanofibers. With the chemical properties, we observed significant tethering of pyridine functionality. The sample, MACNF-7 (10 mL of polymer solution doped with 0.7 g of melamine), provided the optimum melamine doping condition to achieve the highest CO₂ adsorption capacity of 3.15 mmol g⁻¹. The adsorption performance was based on simultaneous improvement in microporosity (physical) and surface basicity (chemical) properties of the adsorbent. However, in a binary mixture with nitrogen, the selective adsorption of CO₂ showed the predominance of the improved surface basicity over microporosity. The highest CO₂ selective capture (1.22 mmol g⁻¹) was occurred for a CO₂:N₂ ratio of 0.15:0.85, with a selectivity of 58.19 at 273 K. In a regeneration test, stable and robust performance was achieved more than five cycles. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47747.     

纳米碳纤维表面非晶态Ni-Fe-Ru-P合金镀层的制备与表征

在铁片试样上研究以次磷酸钠为还原剂的化学镀Ni-Fe-Ru-P合金镀层的工艺,考察了金属盐浓度对化学镀反应沉积速率的影响.利用优化的工艺配方在经过敏化,活化处理后的纳米碳纤维表面沉积Ni-Fe-_Ru-P合金镀层,分别利用EDS、XRD、SEM等手段对镀层的成分,结构,形貌进行了表征,并对其进行了热处理.结果表明,利用化学镀技术可以在纳米碳纤维表面获得连续、均匀的Ni-Fe-Ru-P合金镀层,且镀层为非晶态结构.在350℃以下热处理不会改变镀层的结构,在400℃以上热处理,镀层开始晶化.     

负载型非晶态合金催化剂Ni-Fe-Rh-P/CNFs的制备及其催化性能

研究了化学镀Ni-Fe-Rh-P非晶态合金镀层的工艺,考察了镀液成分和工艺参数对沉积速率和镀层质量的影响。利用优化的工艺配方在经过敏化、活化处理后的纳米碳纤维（CNFs）表面沉积了Ni-Fe-Rh-P合金镀层,分别利用能量色散X射线谱（EDS）、X射线衍射仪（XRD）及扫描电子显微镜（SEM）等手段对镀层的成分、结构、形貌进行了表征,采用液相硝基苯催化加氢反应表征了制备催化剂的催化活性。结果表明,利用化学镀技术可以在纳米碳纤维表面负载连续、均匀的Ni-Fe-Rh-P合金镀层,且镀层为非晶态结构;负载型非晶态合金催化剂Ni-Fe-Rh-P/CNFs具有很高的催化活性和良好的循环使用性能。     

金属有机骨架材料储存CO_2的研究进展

随着温室效应日益严重,研发高效捕获CO_2的新型材料对于缓解环境压力具有重要意义。金属有机骨架材料具有高比表面积、结构多样性和孔道可调控性等优点,尤其在储存CO_2方面展现出惊人潜质。简要介绍金属有机骨架材料及其延伸化合物——沸石咪唑酯骨架材料和共价有机骨架材料作为新型储存CO_2材料,在结构、储存CO_2性能和机理等方面的研究进展,并阐述了该类材料在研究过程中存在的不足与发展前景。     

封存CO2的泄漏过程预测与泄漏速率的影响因素特性

地下封存CO₂泄漏的评估方法和风险控制是碳捕集和封存（CCS）技术亟待解决的核心问题。为了揭示封存CO₂泄漏过程的影响因素及其特性,本文建立两相流驱替过程数学模型描述封存CO₂的泄漏过程,采用COMSOL Multiphysics 3.5a软件进行数值模拟。通过对基准问题及其解的拓展,分别对注入井与泄漏通道之间距离、泄漏通道半径、泄漏通道渗透率、CO₂注入速率和CO2注入深度等因素对封存CO2泄漏过程的影响特性进行研究,通过过程模拟和数据分析得到了影响因素的定量函数关系。研究表明：封存CO₂的渐近泄漏速率与注入井与泄漏通道之间距离倒数呈对数线性关系,与泄漏通道半径呈抛物线型关系,与注入速率呈线性关系;泄漏通道的绝对渗透率是CO₂泄漏速率控制的关键因素,而CO₂注入深度的增加并不能有效地降低CO₂泄漏速率。本文的计算模型和数值模拟结果不仅揭示了地下封存CO₂泄漏过程的影响因素与泄漏速率之间的定量关联规律,还可为地下封存CO₂的封存地点选择、泄漏速率估计和泄漏风险评估提供工程分析方法和计算工具。     

TiO2 nanofibers doped with rare earth elements and their photocatalytic activity

In the present study rare earth doped (Ln³⁺–TiO₂, Ln = La, Ce and Nd) TiO₂ nanofibers were prepared by the sol–gel electrospinning method and characterized by XRD, SEM, EDX, TEM, and UV-DRS. The photocatalytic activity of the samples was evaluated by Rhodamine 6G (R6G) dye degradation under UV light irradiation. XRD analysis showed that all the synthesized pure and doped titania nanofibers contain pure anatase phase at 500 °C but at 700 °C it shows both anatase and rutile phase. XRD result also shows that Ln³⁺-doped titania probably inhibits the phase transformation. The diameter of nanofibers for all samples ranges from 200 to 700 nm. It was also observed that the presence of rare-earth oxides in the host TiO₂ could decrease the band gap and accelerate the separation of photogenerated electron–hole pairs, which eventually led to higher photocatalytic activity. To sum up, our study demonstrates that Ln³⁺-doped TiO₂ samples exhibit higher photocatalytic activity than pure TiO₂ whereas Nd³⁺-doped TiO₂ catalyst showed the highest photocatalytic activity among the rare earth doped samples.     

Synthesis of carbon nanofibers and measurements of hydrogen storage

The synthesis of carbon nanofibers was carried out by catalytic decomposition of ethylene in presence of hydrogen. Bimetallic catalysts, e.g. Fe-Cu or Ni-Cu, were synthesized by coprecipitation, reduction-precipitation and reverse microemulsion techniques and were proven to have a strong influence on the morphology of the nanofibers. The best results in terms of synthesis homogeneity were obtained by supporting the bimetallic catalyst on a high surface area silica support by the “incipient wetness” method. The hydrogen storage capacity of carbon nanofibers was tested in a custom made Sievert apparatus operating up to 160 bar and 450 °C. Several “in situ” activation procedures were experimented, however according to our data carbon nanofibers do not seem a suitable candidate for hydrogen storage. With the purpose of promoting a “spillover” function, 2 wt.% Pd-doped nanofibers were prepared. After loading at 77 bar, a hydrogen storage of 1.38 ± 0.30 wt.% was measured at room temperature.     

CuO/TiO2纳米纤维可见光催化CO2合成甲醇

以介孔SiO_2球为模板、TiCl4为前驱体,采用气相生长法制备了直径为8～10nm的TiO_2纳米纤维,然后采用浸渍法制备了具有异质结结构的CuO/TiO_2纳米纤维,在可见光照射下催化CO_2合成甲醇。通过SEM、TEM、XPS、UV-Vis、XRD、荧光光谱(PL)对催化剂进行了表征。结果表明:TiO_2纳米纤维较锐钛矿TiO_2纳米颗粒和商业TiO_2纳米颗粒(P25)荧光强度明显降低,光生电子-空穴对更加稳定。通过在TiO_2纳米纤维上负载CuO形成异质结结构后,进一步降低了催化剂的荧光强度,也增强了在可见光区的吸收。在300 W氙灯照射5 h进行光催化CO_2合成甲醇实验中,P25负载CuO后,催化合成甲醇产量为676μmol/g-cat,而负载了CuO的TiO_2纳米纤维,甲醇产量达1791μmol/g-cat,较CuO/P25提高了165%。     

Hydrogen storage in multilayer carbon nanotubes

Multilayer carbon nanotubes obtained by pyrolysis and mechanical activation of plant-derived amorphous carbon are excellent sorbents for hydrogen.