Alkali insertion within NiONi electrode in contact with molten Li2CO3K2CO3 and Li2CO3Na2CO3K2CO3 at 650°C

Lithium, sodium and potassium species have been analysed by different spectroscopic techniques in the NiO layer recovering nickel cathode used in the state-of-the-art molten carbonate fuel cell. The nickel electrode was previously oxidized in lithium-containing carbonate electrolytes, Li₂CO₃K₂CO₃ and Li₂C0₃Na₂CO₃K₂CO₃ at 650°C. Similarly to the well-known case of lithium, it has been shown that the presence of sodium and potassium cations could be associated to their insertion in the NiO lattice.     

Effects of ion irradiation on H2O and CO2 absorption and desorption characteristics of Li2ZrO3 and Pt-coated Li2ZrO3

The effects of irradiation with 10 keV D₂⁺ ions on the hydrogen and water absorption and desorption characteristics of Li₂ZrO₃ and platinum-coated Li₂ZrO₃ (Pt-Li₂ZrO₃) were investigated by employing elastic recoil detection (ERD), weight gain measurement (WGM), and thermal desorption spectroscopy (TDS). WGM and ERD results indicated that the amounts of H and H₂O absorbed into the ion irradiated bulk Li₂ZrO₃ and Pt-Li₂ZrO₃ samples in air at room temperature increased up to ～2–3 times, as compared with those of the unirradiated ones. TDS examinations revealed that the amounts of hydrogen molecules (H₂) and H₂O released from the unirradiated Pt-Li₂ZrO₃ and ion irradiated Li₂ZrO₃ and Pt-Li₂ZrO₃ were approximately one order of magnitude higher than those of unirradiated Li₂ZrO₃. Li segregation, ion-induced oxygen deficiency, as well as Pt deposition significantly enhance the splitting of H₂O, eventually increasing the amounts of H accumulated in the bulk Li₂ZrO₃ and the H₂ release.     

Li2CO3-Na2CO3-K2CO3相图的理论预测

熔盐是一种重要的聚光太阳能系统传热流体,多元熔盐混合是满足实际需求的有效方法,而熔盐混合物的相图是其筛选的主要因素之一.该文基于热力学原理及吉布斯自由能对Li2CO3-Na2CO3-K2CO3的相图进行预测与计算,结果显示:该熔盐混合物的共晶点为421.2℃,Li2CO3、Na2CO3和K2CO3的质量分数分别为25....     

应用Na2O2吸收控制汽车尾气中CO2排放物

简述了汽车排放污染物的种类、危害及各种相应的减排控制措施,针对CO2这一温室气体提出了通过Na2O2吸收的解决方案,并给出了CO2吸收器的基本构造和反应机理,同时也指出了这一方案在实际运行中存在的问题。     

The deactivation effect of Na2O and NaCl on CeO2–TiO2 catalysts for selective catalytic reduction of NO with NH3

The effect of Na₂O and NaCl on CeO₂–TiO₂ catalyst for the selective catalytic reduction of NO with NH₃ was investigated with BET, XRD, XPS, NH₃-TPD, H₂-TPR, in-situ DRIFT and catalytic activity measurements. The results showed that both Na species could deactivate the CeO₂–TiO₂ catalyst and Na₂O had a stronger effect than NaCl. The more serious deactivation by Na₂O could be ascribed to smaller surface area, fewer surface Ce³⁺ and chemical adsorbed oxygen, lower surface acidity, and worse reducibility. The introduction of NaCl and Na₂O facilitated the formation of new surface NO_x adspecies, but were inactive in NH₃-SCR reaction. The adsorption of NH₃ were inhibited. The NH₃-SCR reaction over the CeO₂–TiO₂ catalyst was governed by both E-R and L-H mechanisms. The introduction of NaCl and Na₂O didn't change the NH₃-SCR reaction mechanisms.     

Studies on metal oxides suitable for enhancement of the O2-releasing step in water splitting by the MnFe2O4–Na2CO3 system

Reactivities of three metal oxides (Fe₂O₃, TiO₂ and MnO₂) with Na₂CO₃, and of their reaction products with CO₂, have been studied to enhance the O₂-releasing step in the two-step water splitting by the MnFe₂O₄–Na₂CO₃ system. X-ray diffraction analysis and thermogravimetric measurements showed that the reaction of α-Fe₂O₃ with Na₂CO₃ (mole ratio=1:1) completed within 10 min at 1073 K to produce NaFeO₂ (Fe₂O₃+Na₂CO₃→NaFeO₂+CO₂). Also, the regeneration of Fe₂O₃ and Na₂CO₃ proceeded readily by passing CO₂ gas through NaFeO₂ (71% yield). TiO₂ reacted with Na₂CO₃ (mole ratio=1:1) at 1073 K for 1 h to form Na₈Ti₅O₁₄ and Na₂TiO₃ (93% yield). However, in the reaction of the products with CO₂, the starting material (TiO₂) was not reproduced at the temperature range from 673 K to 1073 K, but Na₄Ti₅O₁₂ (having a lower Na content than the form Na₈Ti₅O₁₄) was formed. In the case of MnO₂ with Na₂CO₃ (mole ratio=2:1), Na_0.7MnO_2–2.05 and NaMnO₂ were produced at 1073 K for 1 h (80% yield), but the reaction between these products and CO₂ hardly proceeded.     

低温固体氧化物燃料电池SDC-(Li/Na)2CO3复合电解质材料优化

采用两种工艺(干法和湿法)制备了钐掺杂的氧化铈(SDC)-(Li/Na)2CO3复合电解质,其中碳酸盐的质量分数分别为20%、25%和30%.通过XRO和SEM观察了不同制备工艺和碳酸盐含量的复合电解质材料的物相结构和表面形貌.采用交流阻抗法测量了复合电解质在空气中400～600℃温度范围的电导率.采用于压法制作了基于(SDC)-(Li/Na)2CO3电解质的单电池,并在氢气/燃料中评价了该电池的输出性能.     

Synthesis and electrochemical properties of lithium cobalt oxides prepared by molten-salt synthesis using the eutectic mixture of LiCl–Li2CO3

Lithium cobalt oxide powders have been successfully prepared by a molten-salt synthesis (MSS) method using a eutectic mixture of LiCl and Li₂CO₃ salts. The physico-chemical properties of the lithium cobalt oxide powders are investigated by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), particle-size analysis and charge–discharge cycling. A lower temperature and a shorter time (∼700°C and 1 h) in the Li:Co=7 system are sufficient to prepare single-phase HT-LiCoO₂ powders by the MSS method, compared with the solid-state reaction method. Charge–discharge tests show that the lithium cobalt oxide prepared at 800°C has an initial discharge capacity as high as 140 mA h g⁻¹, and 100 mA h g⁻¹ after 40 cycles. The dependence of the synthetic conditions of HT-LiCoO₂ on the reaction temperature, time and amount of flux with respect to starting oxides is extensively investigated.     

Na2SO3吸收NO2的反应动力学试验研究

为验证湿法烟气脱硫产物溶液还原吸收脱硝技术的可行性,考察了溶液浓度、NO_2分压等不同因素对吸收特性的影响。在搅拌釜系统内进行Na_2SO_3溶液吸收NO_2的反应动力学研究。结果显示:Na_2SO_3溶液吸收NO_2的反应属于快速拟一级反应。NO_2的吸收速率与其入口的NO_2分压呈线性正比关系。NO的生成量随NO_2入口浓度的增加而增加,且NO_2在NaHSO_3溶液中产生的NO量远大于在Na_2SO_3溶液中产生的量。     

Conductivity and parametric studies of a (PEO+(glass)(15Na2O–15NaF–70B2O3)) cell

Ion conducting polymer electrolyte films based on poly(ethylene oxide) (PEO) complexed with a glass (15Na₂O–15NaF–70B₂O₃) are prepared by a solution—cast technique. The complexation of the glass with PEO is confirmed by X-ray diffraction analysis. DC conductivity in the temperature range 303–373 K and transference number measurements are performed in order to investigate the charge transport in the polymer electrolyte system. The conductivity of the (PEO+glass) electrolyte is about 10⁴ times larger than that of pure PEO at room temperature. The transference number data show that the charge transport in this polymer electrolyte system is predominantly due to ions. Using these polymer electrolytes, solid-state electrochemical cells are fabricated. Various parameters associated with these cells are evaluated and compared with those of other reported cells.     

Combined steam and CO2 reforming of methane (CSCRM) over Ni–Pd/Al2O3 catalyst for syngas formation

In order to syngas formation, combined steam and carbon dioxide reforming of methane (CSCRM) used in the presence of Ni–Pd/Al₂O₃ catalysts, which were synthesized by the sol-gel method. Al₂O₃ supported Ni–Pd catalyst exhibited the appropriate surface area of 176.2 m²/g and high dispersion of NiO phase with an average crystallite size of 11 nm, which was detected on catalyst surface utilizing transmission electron microscopy (TEM). The influence of three independent operating parameters including reaction temperature in the range of 500–1000 °C; (CO₂ + H₂O)/CH₄ ratio, in the range of 1–3 and CO₂/H₂O ratio; in the range of 1–3, were investigated on the responses (i.e., CH₄ conversion, H₂ yield, CO yield, amount of coke formation on the catalyst surface and H₂/CO ratio) in CSCRM by using response surface methodology–central composite design (RSM-CCD) method. The obtained results from ANOVA and the proposed quadratic models could fine forecast the responses. It was seen that the total methane conversion and CO yield was almost accessible at temperatures higher than 850 °C. Moreover, the CO₂/H₂O ratio exhibited no significant effect on the CH₄ conversion, H₂ yield and CO yield of Ni–Pd/Al₂O₃ catalysts in CSCRM reaction. However, the high CO₂/H₂O ratio in inlet feed led to the syngas formation with a low H₂/CO ratio. The results revealed that lower CO₂/H₂O ratio and higher temperature as well as higher (CO₂ + H₂O)/CH₄ ratio help to decrease the coke formation.     

Ionic transport and battery characterization studies on NaINa2OB2O3 ternary glassy system

Glasses in the ternary system xNaI-yNa₂O-[100−(x+y)]B₂O₃ prepared by a melt quenching method are characterized by using different experimental techniques such as X-ray diffraction, ionic transference number and conductivity. The conductivity is found to vary in a non-linear manner with change in the NaI/Na₂O ratio. The highest conductivity glass composition is used as an electrolyte in the fabrication of a solid-state electrochemical cell. A decomposition potential of 2.5 V is determined for the electrolyte. The discharge chracteristics of the cell are investigated at ambient temperature and various cell parameters are determined. The open-circuit voltage and short-circuit current of the cell are 2.7 V and 1600 μA, respectively.     

Thermodynamic models for H2O–CO2–H2 mixtures in near-critical and supercritical regions of water

The PVTx properties of the H₂O–CO₂–H₂ mixtures have significant applications in the technology of supercritical water gasification of coal. Here, we first carry out the molecular dynamics simulations of the PVTx properties of the H₂O–CO₂–H₂ mixtures in the near-critical and supercritical regions of water to generate 600 datasets at 750–1150 K and 4.0–443.5 MPa. The molar fraction of each composition in the ternary mixtures ranges from 10% to 80%. Later we investigate the applicability of a well-known thermodynamic model for the ternary mixtures, namely the Duan-Møller-Weare equation of state (DMW EOS). It is observed that the DMW EOS shows great potential in the prediction of the PVTx properties of the ternary mixtures. However, it is noted that the mixing parameters describing the binary interactions of H₂O–H₂ and CO₂–H₂ are still unknown in the DMW EOS. By determining the missing mixing parameters using the Levenberg-Marquardt algorithm, the accuracy of the original DMW EOS is improved for the ternary mixtures. Moreover, optimizing the coefficients in the DMW EOS further promotes the accuracy of the model for the H₂O–CO₂–H₂ mixtures. The results from this work may facilitate the development of supercritical water gasification of coal.     

CO2 reforming of methane over NixMg6−xAl2 catalysts: Effect of lanthanum doping on catalytic activity and stability

Ni_xMg_6?xAl₂ and Ni_xMg_6?xAl_1.8La_0.2 (x = 2, 4 or 6) catalysts were prepared via a co-precipitation method and calcined under an air flow at 800 °C. X-ray diffraction (XRD) results showed that the Ni_xMg_6?xAl_1.8La_0.2 catalysts contained different lanthanum oxide species after calcination. Fourier Transform Infrared Spectroscopy (FTIR) spectra demonstrated that the lanthanum doped catalysts adsorbed more CO₂ compared to the lanthanum free solids. This improved basicity was verified in the CO₂-TPD profiles. Temperature programmed reduction (TPR) analyses proved that the addition of lanthanum affected nickel species distribution in the catalysts and strengthened NiO-MgO interactions inside the solid matrix. The CO₂ reforming of methane reaction (Ar/CO₂/CH₄:60/20/20; GHSV 60000 mL g^?1 h^?1) was carried out over the different catalysts in the temperature range of 600 °C–800 °C. Lanthanum addition improved the catalytic activity particularly by favoring the methane dry reforming reaction over all the other secondary reactions in addition to the creation of more basic sites that enhanced CO₂ adsorption and contributed to the removal of carbon deposits. The most active lanthanum containing catalyst kept a constant catalytic performance for 14 h on stream despite the formation of carbon deposits. These carbon deposits can be removed under an oxidative atmosphere at moderate temperature due to the presence of lanthanum oxide species in the catalyst.     

On the growth of Li2CO3 dendrites in nickel–cadmium industrial batteries

A large amount of Li₂CO₃ dendrites has been detected on positive electrodes in Ni–Cd industrial pocket plate batteries, intended to work in stationary applications, after 3 years in float charge. The lattice parameters were refined to a=8.353(1) Å, b=4.974(1) Å, c=6.194(1) Å and β=114.6(1)° [monoclinic], which is in complete agreement with structural data reported in the literature. Oxidation of graphite present in the positive active material is enhanced at elevated temperatures, and at high anodic potentials. This results in an extremely high carbonate concentration in the active material, as well as in the electrolyte. The high carbonate content, in combination with the relatively high lithium concentration present in both electrolyte and positive electrode, is very likely to be the reason for the formation of the Li₂CO₃ dendrites. As this process continues, agglomerates of the dendrites in combination with attached β-Cd(OH)₂ and graphite may generate short circuits between the positive and the negative electrodes.     

Hydrogen ion sensing characteristics of Na3BiO4–Bi2O3 mixed oxide nanostructures based EGFET pH sensor

In the present paper, Na₃BiO₄–Bi₂O₃ films have been tested for hydrogen ion sensing. Na₃BiO₄–Bi₂O₃ mixed oxide nanostructures were deposited on the Indium–Tin-Oxide (ITO) coated glass substrate using a low-cost electrodeposition technique at room temperature. The nanostructures have been characterized using FESEM and XPS to study their morphology and composition, respectively. Vertically aligned nanostructures (thickness~90 nm) with well-defined edges were seen in FESEM studies. XPS analysis indicates the presence of Na₃BiO₄ and Bi₂O₃. The crystallinity and the mixed phase of the film were further confirmed by X-ray diffraction study. These nanostructures were explored as a potential candidate for pH sensing using them as a sensing film for Extended-Gate Field-Effect Transistor (EGFET). A sensitivity of 49.63 mV/pH has been observed with good linearity. To the best of our knowledge, for the first time vertically aligned Na₃BiO₄–Bi₂O₃ mixed oxide nanostructures are demonstrated as an EGFET-based (Hydrogen ion) pH sensor.     

Correlation between CO surface coverage and selectivity/kinetics for the preferential CO oxidation over Pt/γ-Al2O3 and Au/α-Fe2O3: an in-situ DRIFTS study

We present in-situ IR (DRIFTS) measurements on CO adsorption and preferential CO oxidation (PROX) in H₂-rich gas on Pt/γ-Al₂O₃ and Au/α-Fe₂O₃ catalysts at their envisaged operating temperatures of 200°C and 80°C, respectively, which in combination with kinetic data show that the underlying reason for the very different PROX reaction kinetics on these two catalysts is the difference in steady-state CO coverage. Whereas on the platinum catalyst this is always near saturation under reaction conditions, causing a negative reaction order (−0.4) and a p_CO-independent selectivity, the amount of adsorbed CO on the gold particles (indicated by an IR band at ∼2110 cm⁻¹) strongly depends on the CO partial pressure. From the position of the IR band of CO adsorbed on Au/α-Fe₂O₃, the steady-state coverages on the Au surface are shown to be significantly below saturation, with an upper limit of approximately θ_CO=0.2. Low reactant surface concentrations on Au explain the positive reaction order with respect to p_CO (+0.55 at 80°C) as well as the observed decoupling of the CO and H₂ oxidation rates, which results in a loss of selectivity with decreasing p_CO.