Electrochemical hydrogen storage and usage aspects: Nickel electrode in acidic electrolyte

The conditions of electrochemical formation of nickel hydride are investigated. The electrochemical properties of different nickel-based materials (bulk, porous, foamed tapes) are examined to state the hydrogen adsorption/absorption phenomena and possibility to use them as a negative electrode in hydrogen devices (electrolyzers, rechargeable batteries, fuel cells). Surface activation of nickel materials are made by electroplating and etching methods. Thin palladium coating is used to prove the formation of nickel hydride during cathodic charging. Volt-amperometric and kinetic measurements show that not only palladium, but also activated nickel plays important role in the surface activation of electrode materials and promotion of hydrogen absorption in nickel substrate materials. Published in Russian in Elektrokhimiya, 2007, vol. 43, No. 5, pp. 624–629. Based on the paper delivered at the 8th Meeting “Fundamental Problems of Solid-State Ionics, Chernogolovka (Russia), 2006. The text was submitted by the authors in English.     

Effect of LiH on electrochemical hydrogen storage properties of Ti55V10Ni35 quasicrystal

The electrochemical hydrogen storage properties and mechanisms of the Ti₅₅V₁₀Ni₃₅ quasicrystal + xLiH(x = 3, 6 and 9 wt.%) system are investigated and discussed in this paper. A composite material in the Ti₅₅V₁₀Ni₃₅ quasicrystal and system has been synthesized moderately by means of mechanical milling under an argon atmosphere, which can avoid reaction of releasing of hydrogen during the process of milling. The results indicate that the addition of LiH significantly improves the electrochemical characteristics of composite material. The maximum discharge capacity increases from 220.1 mAh/g to 292.3 mAh/g on Ti₅₅V₁₀Ni₃₅ + 6 wt.% LiH, and the cycling stability is also enhanced too. In addition, the high rate dischargeability (HRD) is ameliorated remarkably, and the value of HRD value at 240 mA/g rises by 78.1%–87.8% for Ti₅₅V₁₀Ni₃₅ + 6 wt.% LiH alloy electrodes. The improvement of characteristics of the electrochemical hydrogen storage characteristics may be attributed to LiH, which has excellent electrochemical activity.     

Electrochemical hydrogen storage in TiC0.6, not in TiC0.9

We demonstrate that hydrogen can be electrochemically loaded, at room temperature, in the non-oxide ceramic TiC_0.6. A capacity of 2.9 wt.% is easily reached, corresponding to the formula TiC_0.6H_1.6. We also demonstrate that hydrogen absorption was not possible in TiC_0.9. This surprising result is interpreted in terms of absence of long-range ordered carbon vacancies, contrary to TiC_0.6. It seems that TiC_0.6 behaves like an intercalation compound for hydrogen.     

Carbon paste electrodes: correlation between the electrochemical hydrogen storage capacity and the physicochemical properties of carbon blacks

The difficulties in the use of carbon paste electrodes to quantify the electrochemical adsorption of hydrogen in nanocarbon materials are described. Chronoamperometry studies using a Ferro/Ferri redox couple were performed to obtain the electrochemical active area of paste electrodes prepared by dispersion of differing samples of carbon blacks (CB) within silicon oil. This electrochemical active area was combined with the BET-surface area of the carbon blacks, to obtain the mass of superficial carbon involved in the electrochemical processes. To assure equal conditions for comparison, the electronic conductivity of the paste was equivalent in all the samples. From our results it appears that cyclic voltammetry, combined with carbon paste electrodes and nitrogen adsorption isotherms, provides a simple and less expensive route for the qualitative evaluation of the electrochemical hydrogen uptake of novel carbon materials. Still, for quantitative measurements, some issues remain unsolved in highly structured carbons, where the lack of penetration of the bulky Ferro/Ferri redox couple in the micropores of the CB and the occurrence of solid-state diffusion cause the underestimation of the mass involved in hydrogen adsorption.     

Na_(0.44)MnO_2在碱性溶液中的电化学机制

Na_(0.44)MnO_2具有原料丰富、合成简单、无毒环境友好、结构稳定性高等优势,适合作为水溶液钠离子电池的正极材料。Na_(0.44)MnO_2在中性水溶液中的比容量较低(30–40m Ah·g~(-1)),而采用碱性电解液可大大提高Na_(0.44)MnO_2的可逆比容量(80 m Ah·g~(-1))。当我们扩宽碱性电池的充放电窗口(1.95–0.3V)时,在1.0V(vsZn/Zn~(2+))附近出现一个宽的放电平台,且首周放电比容量高达275 m Ah·g~(-1),远远超出其理论嵌钠容量(121 m Ah·g~(-1))。本文我们通过对不同放电深度下的电极进行X射线粉末衍射仪(XRD)、扫描电子显微镜(SEM)和电感耦合等离子体发射光谱(ICP-AES)表征,研究其超额容量的放电机理。结果表明1.0 V以下的低电位放电过程可分为两个阶段:第一阶段为H+在隧道结构中的嵌入,此时隧道结构保持不变,放电曲线上表现为平台区;第二阶段为过量H+的嵌入引起隧道结构破坏,同时伴随着Mn(OH)_2相的生成和Na+从结构中释放出来,放电曲线上表现为斜坡区。这一研究结果表明Na_(0.44)MnO_2在碱液中的可逆性与下限电位紧密相关,高稳定的Na_(0.44)MnO_2材料需要避免H+的嵌入。     

Capacitive performance of ordered mesoporous carbons with tunable porous texture in ionic liquid electrolytes

Ordered mesoporous carbons with tunable pore size and surface chemical properties are prepared by doping boric acid using a hard-templating method. The capacitive performance of these carbons is investigated in two common ionic liquids of EMImBF₄ and EMImTSFI. As demonstrated by the structure analysis, the pore size increases from 3.3 to 5.7 nm and the content of oxygenated groups on the carbon surface increases from 2.0 to 5.2 mol% with the increase of the boron doping from 0 to 50 mol%. In ionic liquid electrolyte, the carbons mainly show typical electric double layer capacitance, and the capacitance retention ratio and ion diffusion in the carbon channels is determined to the surface chemical property. The prepared carbons present visible pseudo-capacitance due to the rapid redox reactions of the oxygenated groups in hydrophilic EMImBF₄, reflecting by the increasing of the specific surface capacitance, while no visible pseudo-capacitive behavior was observed in hydrophobic EMImTSFI.     

Tuning the physisorption of molecular hydrogen: binding to aromatic,hetero-aromatic and metal-organic framework materials

We present a study on the binding properties of molecular hydrogen to several polar aromatic molecules and to a model for the metal-oxide corner of the metal organic framework materials recently investigated as promising supports for hydrogen storage. Density functional theory employing the Perdew Wang exchange-correlation functional and second order Møller-Plesset calculations are used to determine the equilibrium structures of complexes with molecular hydrogen and their stability. It is found that for most hetero-aromatics the edge sites for molecular hydrogen physisorption have stabilities comparable to the top sites. The DFT predicted binding energies compare favorably with those estimated at MP2 level, and get closer to the MP2 results for increased electrostatic contributions (induced by the polar aromatics) to the intermolecular interaction. Vibrational frequencies are also computed at the DFT level, and infrared activities of the H₂ stretching frequency are compared for the various complexes. Pyrrole, pyridine and n-oxide pyridine are predicted to form the more stable complexes among one-ring aromatics. The computed binding energies to metal-organic framework materials are in good agreement with experimental observations. It is suggested that replacement of the organic linker in MOF materials with some of the more efficient aromatics investigated here might contribute to enhance the H₂ storage properties of mixed inorganic–organic materials.     

Fe部分替代Cu对低钴AB_5型贮氢合金相结构和电化学性能的影响

为了获得既具有较高电化学容量又具有良好循环稳定性的低钴AB5型贮氢合金,研究了Fe部分替代Cu对低钴AB5型贮氢合金相结构和电化学性能的影响.采用真空感应熔炼方法,制备了一系列含Cu和Fe的低钴AB5型贮氢合金LaNi3.55Mn0.35Co0.20Al0.20Cu0.85-xFex(x=0.10,0.20,0.25,0.40,0.60).粉末X射线衍射(XRD)分析表明,合金含有单一CaCu5型六方结构的LaNi5相,Fe部分替代Cu并没有改变合金的本体相结构,但随着Fe含量的增大,晶格参数a,c和晶胞体积V增大.电化学性能测试表明,随着x增加,合金的放电容量和高倍率放电能力降低,但是循环稳定性得到了显著提高.当x从0.10增加到0.60时,合金的200周循环稳定性(S200)从77.6%提高到89.9%.Fe替代Cu有利于提高合金的循环稳定性,这主要是随着Fe替代量增大,晶胞体积增大,晶格体积膨胀率明显减小,合金的抗粉化能力增强.     

Nickel hydrogen gas batteries: From aerospace to grid-scale energy storage applications

The challenging requirements of high safety, low-cost, all-climate and long lifespan restrict most battery technologies for grid-scale energy storage. Historically, owing to stable electrode reactions and robust battery chemistry, aqueous nickel–hydrogen gas (Ni–H₂) batteries with outstanding durability and safety have been served in aerospace and satellite systems for over three decades ever since their first development in the 1970s. Despite their satisfactory performances, this technology has difficulty to be applied for grid-scale energy storage primarily because of their high cost resulting from the utilization of expensive platinum as anode hydrogen catalyst. In recent years, with the extensive exploration of inexpensive hydrogen evolution/oxidation reaction catalysts, advanced Ni–H₂ batteries have been revived as promising battery chemistry for grid-scale energy storage applications. This mini-review provides an overview of the development activities of Ni–H₂ batteries and highlights the recent advances in the application of advanced Ni–H₂ batteries for grid-scale energy storage. New cost-effective hydrogen evolution/oxidation reactions catalysts, novel cathode materials, and advanced Ni–H₂ battery designs toward further development of Ni–H₂ batteries are discussed. The renaissance of advanced Ni–H₂ battery technology is particularly attractive for future grid-scale energy storage applications.     

电化学储能研究22年回顾

本文回顾了22年来作者的电化学储能研究活动,共分三个部分. 第一部分叙述高比能量、高比功率储能器件研究,包括锂硫电池研究（硫复合正极材料、锂硫电池制作、锂硼合金作为锂硫电池负极、硫-锂离子电池新体系）、超级电容器研究（超级活性炭、以酚醛树脂为原料制备电容炭、碳纳米管阵列中寄生准电容储能材料、氧化镍干凝胶准电容储能材料、归纳出电容炭材料的性能要求、电容器研制、确定“第四类”超级电容器）、锂离子电池研究（锂离子电池与可再生燃料电池的对决、双变价元素正极材料、磷酸钴锂正极材料、高功率锂离子电池的制作）. 第二部分叙述规模储能电池研究,包括液流电池新体系研究（蓄电与电化学合成的双功能液流电池、全金属化合物单液流电池、有机化合物正极的单液流电池）、致力于振兴铅酸电池（推广铅蓄电池新技术、铅炭电池的研究、铅酸电池新型板栅的研究）,储能电池（站）的经济效益计算方法. 第三部分叙述电动汽车发展路线研究,包括氢能燃料电池电动汽车、纯电动汽车与混合动力汽车、对我国电动汽车发展路线的建议、力争电动汽车补贴的合理化、坚守电动汽车“节能减排”宗旨、提出“发电直驱电动车”. 最后的结束语谈了三点感悟.     

Synthesis, X-ray crystal structures, and gas sorption properties of pillared square grid nets based on paddle-wheel motifs: implications for hydrogen storage in porous materials

A systematic modulation of organic ligands connecting dinuclear paddle-wheel motifs leads to a series of isomorphous metal-organic porous materials that have a three-dimensional connectivity and interconnected pores. Aromatic dicarboxylates such as 1,4-benzenedicarboxylate (1,4-bdc), tetramethylterephthalate (tmbdc), 1,4-naphthalenedicarboxylate (1,4-ndc), tetrafluoroterephthalate (tfbdc), or 2,6-naphthalenedicarboxylate (2,6-ndc) are linear linkers that form two-dimensional layers, and diamine ligands, 4-diazabicyclo[2.2.2]octane (dabco) or 4,4'-dipyridyl (bpy), coordinate at both sides of Zn(2) paddle-wheel units to bridge the layers vertically. The resulting open frameworks [Zn(2)(1,4-bdc)(2)(dabco)] (1), [Zn(2)(1,4-bdc)(tmbdc)(dabco)] (2), [Zn(2)(tmbdc)(2)(dabco)] (3), [Zn(2)(1,4-ndc)(2)(dabco)] (4), [Zn(2)(tfbdc)(2)(dabco)] (5), and [Zn(2)(tmbdc)(2)(bpy)] (8) possess varying size of pores and free apertures originating from the side groups of the 1,4-bdc derivatives. [Zn(2)(1,4-bdc)(2)(bpy)] (6) and [Zn(2)(2,6-ndc)(2)(bpy)] (7) have two- and threefold interpenetrating structures, respectively. The non-interpenetrating frameworks (1-5 and 8) possess surface areas in the range of 1450-2090 m(2)g(-1) and hydrogen sorption capacities of 1.7-2.1 wt % at 78 K and 1 atm. A detailed analysis of the sorption data in conjunction with structural similarities and differences concludes that porous materials with straight channels and large openings do not perform better than those with wavy channels and small openings in terms of hydrogen storage through physisorption.     

Redox flow batteries for energy storage: Recent advances in using organic active materials

The development of redox electrolytes using organic active materials as alternatives to metal-based species for redox flow batteries is booming recently. However, challenges and gaps remain toward commercialization. This review briefly discusses the most recent advances of using electroactive organic materials. Strategies such as chemical modification through molecular engineering and new efforts toward energy-rich electrolytes and high-power electrolytes are addressed. Furthermore, the limiting factors governing the cycling life are summarized.     

Studying the process of ionization of hydrogen in conditions of its forced delivery to a porous nickel oxide electrode

The hydrogen ionization process is studied experimentally on an industrial sintered nickel oxide electrode in models of sealed nickel-metal hydride batteries. It is shown that the hydrogen ionization rates that are reached during overcharge by high current densities in conditions of forced gas delivery into the electrode pores (up to 40 mA cm^?2) exceed the self-discharge rate of a nickel-hydrogen battery by two orders of magnitude. Up to 70% of hydrogen delivered into the compact assembly block undergoes ionization during forced charge of models of sealed nickel-metal hydride batteries with a closed hydrogen cycle. Two independent methods (potentiostatic and manometric) are used to determine the relationship between rates of hydrogen ionization with the degree of the electrode filling with gas and perform estimation of the process intensity at a unit reaction surface. It is established that, in conditions of forced gas delivery, practically all the hydrogen oxidation current is generated at the surface of the nickel oxide electrode beneath thin films of an electrolyte solution at the rate of 4–5 mA cm^?2. It is shown that the hydrogen oxidation rate on a nickel oxide electrode filled in part by gas is independent of the electrode potential, probably because of a tangible contribution made by diffusion limitations to the overall hampering of the process.     

NaOH电解液改善MH/Ni电池自放电性能的机理研究

以NaOH电解液代替KOH能够明显改善MH/N i电池的自放电性能和高温(60℃)充电效率.电化学阻抗和循环伏安测试表明,NaOH电解液的作用可能是改变了H原子于负极表面的吸(脱)附行为,并在一定程度上抑制了负极的析氢过程,从而改善了电池的自放电性能.