Hydrogen production from methane and carbon dioxide mixture using all-solid-state electrochemical cell based on a proton-conducting membrane and redox-robust composite electrodes

In recent years, interest in hydrogen as a fuel has sharply increased in the field of alternative and green energy due to its high energy capability and zero-emission behaviour. As a result, research in the development of new highly efficient methods for producing high-purity hydrogen is relevant. This paper presents, for the first time, the test results of an electrochemical cell with a proton-conducting La_(0.9)Sr_(0.1)ScO_(3-δ) electrolyte and symmetrical Sr_(1.95)Fe_(1.4)Ni_(0.1)Mo_(0.5)O_(6-δ)+ La_(0.9)Sr_(0.1)Sc_(0.9)Co_(0.1)O_(3-δ) electrodes as a hybrid setup for electricity generation in proton ceramic fuel cell mode, for hydrogen separation from H_(2)+ Ar mixture and the production of high-purity hydrogen from methane with simultaneous CO_(2) utilization.It was found that this electrochemical cell generates high flow rates of hydrogen during its separation through a proton-conducting membrane from H_(2)+ Ar mixture, about 500 cm^(3)h^(-1)cm^(-2)at a current density of 0.6 A cm^(-2)as well as about 370 cm^(3) h^(-1)cm^(-2)at a current density of 0.5 A cm^(-2) from CH_(4)+ CO_(2) mixture at 800 ℃ which shows that these cells are promising for hydrogen production.

Atomically Dispersed Ruthenium Catalysts with Open Hollow Structure for Lithium-Oxygen Batteries

Lithium–oxygen battery with ultrahigh theoretical energy density is considered a highly competitive next-generation energy storage device,but its practical application is severely hindered by issues such as difficult decomposition of discharge products at present.Here,we have developed N-doped carbon anchored atomically dispersed Ru sites cathode catalyst with open hollow structure(h-RuNC)for Lithium–oxygen battery.On one hand,the abundance of atomically dispersed Ru sites can effectively catalyze the formation and decomposition of discharge products,thereby greatly enhancing the redox kinetics.On the other hand,the open hollow structure not only enhances the mass activity of atomically dispersed Ru sites but also improves the diffusion efficiency of catalytic molecules.Therefore,the excellent activity from atomically dispersed Ru sites and the enhanced diffusion from open hollow structure respectively improve the redox kinetics and cycling stability,ultimately achieving a high-performance lithium–oxygen battery.

Gas Purification and Quality Control of the End Gas Product

One of the main problems in the flow-through gas purification technologies is related with continuous control of the outlet gas purity. The information concerning purity of the produced gas is on high demand, e.g., for processing systems integrated with gas purifiers. The positive solution of this problem has become possible only now due to the appearance of reactive getters (reactants) that serve as highly efficient sinks for gas impurities and our sorption model of the processes, which take place in gas purifiers with these reactants. According to the given model the appearance of a single valued functional connection between the purity of the gas product and the duration of the treatment of the gas flow by the sorbing powder is typical for any system Me -Y, where Me is a powder reactant and Y is an impurity gas. This strict correlation provides the mathematical justification to a simple method of determining the concentration of the impurity in the gas flow at the exit from the gas purifier. This method comes down to measuring of the quantity of the purified gas by a gas flow meter, the readings of which are graduated in the units of gas concentration.

Uranium in Saline Lakes of Mongolia and Adjacent Areas

1 Introduction Increasing demand for uranium raw materials for the nuclear industry has stimulated interest in non-traditional sources,including hydromineral ones[Qin,2009].Those are saline lakes located in the uranium ore districts.Accumulation of uranium in such lakes results from the leaching of uranium from the rocks by surface and ground

Mechanochemical Methods in the Production of High Purity Gases

The development of advanced and cost-effective methods is of prime importance for manufacturers of high purity gases. In this paper a new strategy in the development of gas flow purification technologies is described, where instead of adsorbents reactants are used, in which not only the surface is used in gas capturing but the entire volume of the material. Moreover, the reactants are activated in the gas flow by a controlled mechanical tool, which keeps the sorption kinetics at the required highest level and reduces the unproductive losses of the consumed reactant almost to zero. The advantages of the method are demonstrated with the examples of two novel gas purification units that are distinguished with uncomplicated design, serviceability and ultimately high purification efficiency.

Thermodynamic Model of Uranium and Arsenic Accumulation in Saline Lakes

1 Introduction The attractiveness of Shaazgai-Nuur Soda Lake(pH9.2-9.4)as an alternative metal source is explained by the high concentration of dissolved uranium(~1 mg/l)due to the location of water drainage territory within the Tsagan-

Factors and mechanisms of chemical composition formation of saline lakes in West Mongolia

All the lakes are accumulative systems for the various chemical elements.However,the ratios of the elements in different lake types are very different.It is generally accepted that the composition of lake water determined by

Biogeochemical conversion of sulfur species in saline lakes of Steppe Altai

The aim of the present research is to identify the main mechanisms of sulfur behavior in saline lakes in the course of time and followed transformations in their chemical composition. The influence of water on chemical composition of biochemical processes involved in decomposition of organic matter was determined by the study of behavior of reduced forms of sulfur in lakes. The determination of reduced forms of sulfur was carried out by successive transfer of each form of sulfur to hydrogen sulfide followed by photometric measurements. The other chemical components were determined by standard methods(atomic absorption, potentiometric method, titration method and others). The salt lakes of the Altai steppe were studied in summer season 2013–2015. Analysis of the chemical composition of the saline lakes of Altai Krai has shown that carbonate-, hydrocarbonate-and chloride ions dominate among anions; sodium is main cation; sulfates are found in subordinate amounts. Reduced forms of sulfur occur everywhere: hydrogen and hydrosulfide sulfur S^(2-) prevail in the bottom sediments; its derivative—elemental S^0—prevails in the lakes water. The second important species in water of soda lakes is hydrosulfide sulfur S^(2-), and in chloride lakes is thiosulfate sulfur S_2O_2^(3ˉ). The lag in the accumulation of sulfates in soda lakes in comparison to chloride lakes can be explained by their bacterial reduction, followed by the formation and deposition of iron sulfides in sediments. In chloride lakes gypsum is a predominantly barrier for sulfates.

Chemical composition and sulfur forms in saline lakes of Kulunda Plain(Russia)

1 Introduction On the territory Kulunda Plain,located to the south-west of the Ob’plateau,there are more than 3,000 fresh and salt lakes with water TDS range from 1 to 430 g/L.The interest in these lakes was associated mainly with the study of

Kinetics and Mechanism of Spontaneous Crystallization of Potassium Nitrate from Its Supersaturated Aqueous Potassium Nitrate from Its Supersaturated Aqueous Solutions

Kinetics of spontaneous crystallization of potassium nitrate from its supersaturated aqueous solutions has been studied simultaneously by electrical conductance and optical transmittance methods. It was found that spontaneous crystallization of potassium nitrate was accompanied by aggregation of crystals. Growth of salt crystals was in the kinetic mode of the growth process, and was described by the equation of the first order regarding supersaturation of solution. The mechanism of aggregation and intergrowth of crystals during bulk crystallization via formation of nucleus-bridges between crystals found earlier for several salts was confirmed. Specific surface energy of potassium nitrate was evaluated on the basis of the above mechanism of aggregation and intergrowth of crystals. The established value of the specific surface energy was reasonable and agreed satisfactorily with the available literature data. Examination of crystal deposit after completion of crystallization allowed detecting crystal agglomerates of freakish and irregular forms, which may be considered as the direct confirmation of the above mechanism of intergrowth of crystals. Kinetics of crystallization, aggregation and size distribution of salt crystals after completion of crystallization have been satisfactory described by the earlier proposed model of the crystallization process. An excellent agreement was established between the experimental data on potassium nitrate solubility in aqueous solutions found in the present work and those available in the literature.

Reactive Alloys of IIA Metals: Gas Sorption and Corrosion as One Process

The present work summarizes the results of previously known, as well as the latest sorption measurements, which were carried out on IIA metal alloys in the form of films, powders and macrobodies with a monolithic structure. Analysis of these data made it possible to construct an empirical sorption model, according to which the corrosive decomposition of reactive alloys is one of the driving forces of the sorption process. This model provides a qualitative description of the sorption behavior of these alloys in a gas environment and can be useful in solving practical problems in the field of vacuum and gas technologies.

Semi-empirical estimation for enhancing negative thermal expansion in PbTiO_(3)-based perovskites

Generally,most materials expand when heated and contract when cooled,whereas negative thermal expansion(NTE)materials are very rare.As a typical NTE material,PbTiO_(3) and related compounds have drawn particular interest in recent years.The discovery of an enhanced NTE system in PbTiO_(3) is beneficial to deepen our understanding of its mechanism and regulate its properties.At present,the method of discriminating an enhanced NTE material based on PbTiO_(3) is not universal.Here,we propose a semi-empirical method through evaluating the average lattice distortion in related systems to estimate the relative coefficient of thermal expansion conveniently.The rationality of the method was verified by the analysis of the 0.6PbTiO_(3)-0.4Bi(Ga_(x)Fe_(1-x))O_(3) system.So far,all PbTiO_(3)-based compounds with enhanced NTE conform well to this method.This method provides the possibility to find more enhanced NTE PbTiO_(3)-based materials.

Thermodynamically controllable synthesis of ZIF-8 exposing different facets and their applications in single atom catalytic oxygen reduction reactions

The development of thermodynamically controllable synthetic strategy to manipulate the morphology of ZIF-8 without capping agent is essential to help understanding their facet effect and the structure-activity relationship of single atom catalysts derived from ZIF-8.Here,we prepared ZIF-8 with different morphologies(cube,truncated rhombododecahedral and rhombododecahedral)and thus area ratio of exposed{100},{110}facets by a thermodynamically controllable synthetic strategy.When the reaction proceeds under room temperature(30℃),the assembling of ZIF-8 followed an area-reducing layered growth mode,while switched to an integral layered growth mode at lower temperature-40℃.Moreover,this strategy also works to obtain ZIF-8 encapsulated with metal precursors(Fe(acac)_(3),Cu(acac)_(2)and Co(acac)_(2)).Single Fe atom anchored on nitrogen doped carbon catalysts(SA-Fe/CN)derived from Fe-ZIF-8 retain their original morphologies and the unsaturated surface-active sites on{100}facet,which further displays different catalytic performance towards oxygen reduction reaction(ORR).This work not only reveals the different growth pattern of ZIF-8,but also points out a new direction for designing and synthesizing MOFs with different morphology rationally.

Neutron diffraction study on anomalous thermal expansion of CrB_(2)

Thermal expansion is an essential issue in the field of materials science and engineering.Investigation of anomalous thermal expansion is beneficial to controlling it and developing related functions.Here,we report disitinctly anisotropic thermal expansion of CrB_(2)via temperature dependence of neutron diffraction,in which positive thermal expansion is observed within basal plane whereas negative thermal expansion emerges along the c direction.Intriguingly,zero thermal expansion of unit cell volume is determined from 5 to 130 K with the coefficient of thermal expansion ofāv=0.4(1)×10^(-6)K^(-1).Magnetization measurement shows there is an antiferromagnetic-paramagnetic transition near 90 K,which may correlate to the thermal expansion anomaly.DFT calculations identify no chemical binding of Cr-Cr pair,implying such antiferromagnetic ordering originates from the double exchange interaction of Cr-B-Cr.

Reactive SPS of Al_(2)O_(3)–RE:YAG(RE=Ce;Ce+Gd)composite ceramic phosphors

Ultrafine-grained Al_(2)O_(3)–rare earth:yttrium aluminium garnet(Al_(2)O_(3)–RE:YAG)(RE=Ce;Ce+Gd)composite ceramics were obtained for the first time by reactive spark plasma sintering(SPS)using commercially available initial oxide powders.The effect of key sintering parameters(temperature,dwell time,and external pressure(P_(load)))on densification peculiarities,structural-phase states,and luminescent properties of composites was studied comprehensively.Differences in phase formation and densification between Ce-doped and Ce,Gd-codoped systems were shown.Parameters of reactive SPS,at which there is partial melting with the formation of near-eutectic zones of the Al_(2)O_(3)–YAG system/coexistence of several variations of the YAG-type phase,were established.Pure corundum–garnet biphasic ceramics with an optimal balance between microstructural and luminescence performance were synthesized at 1425℃/30 min/30–60 MPa.The external quantum efficiency(EQE)of the phosphor converters reached 80.7%and 72%with close lifetime of~63.8 ns,similar to those of commercial Ce:YAG materials,which is promising for further applications in the field of high-power white light-emitting diodes(WLEDs)and laser diodes(LDs).

Co-milling as a synergy factor for co-firing.A case study of wood/coal blends

It is known that simple adding of wood allows one to accelerate the ignition of powder mixtures compared to the situation when pure coal is used.This study focuses on testing the hypothesis about the effect of co-milling coal and wood on their co-firing:is the case of composite powdered fuels should ensure the maximum possible efficiency of heat and mass transfer?Firstly,we will show that co-milling of coal and wood leads not independent size reduction of two materials but gives composite powder-coal-covered wood.For the composite fuel further reduction of the ignition delay time of air suspension and reduction of the limit volume concentration required for flame propagation have demonstrated.Obtained synergy also manifests in thermogravimetry.Here we propose a simple method for analyzing the mass loss curves.For any coal-to-wood sawdust ratio,combustion of the composites and mixtures both can be viewed as a weighted sum of the curves of individual components.But only in the case of composites calculated sawdust content is higher than the actual one:the mass loss is redistributed towards the stage occurring at lower temperatures due to geometry of wood/coal contact.

Optimizing geometric configuration of single Zn-N_(4) sites for boosting reciprocal transformation between aromatic alcohols and aldehydes

It is significant to optimize geometric configuration of metal catalytic sites and boost their catalytic activity.Herein,we synthesized isolated single Zn-N_(4)sites on N-doped carbon(Zn-CN)by pyrolyzing zeolite imidazole framework-8(ZIF-8)at different temperatures.For the reciprocal transformation between benzyl alcohol and benzaldehyde,the catalytic activities of Zn-CN catalysts exhibited a volcano-like trend as the pyrolysis temperatures increased.The optimal catalyst was Zn-CN-900,with outstanding catalytic activity exceeding commercial 20 wt.%Pd/C and 20 wt.%Pt/C,promising to substitute the noble metalbased catalysts.X-ray absorption near-edge structure(XANES)measurements and density functional theory(DFT)calculation revealed the gradual transformation from tetrahedral ZnN_(4)sites of ZIF-8 into planar ZnN_(4)sites above 700℃,with the maximum planar ZnN_(4)sites in Zn-CN-900.The stronger adsorption between reactants and planar ZnN_(4)sites facilitated the activation of reactants compared with tetrahedral ZnN_(4)sites.This work will provide valuable insight into rational design of efficient catalysts by optimizing geometric configuration of catalytic sites.

Microtubular solid oxide fuel cells with a two-layer LSCF/BSCFM5 cathode

In this study,we present the development of microtubular solid oxide fuel cells(MT-SOFC)with a two-layer cathode:a composite cathode functional layer(CFL)adjacent to the buffer layer(BL)and a cathode current-collecting layer(CCCL).CFL consists of a mixture of BL material Ce_(0.9)Sm_(0.2)O_(1.95)(SDC)and perovskite Ba_(0.5)Sr_(0.5)Co_(0.75)Fe_(0.2)Mo_(0.05)O_(3-δ)(BSCFM5),which has a high exchange rate with oxygen.The widely used cathode material La_(0.6)Sr_(0.4)Co_(0.2)Fe_(0.8)O_(3-δ)(LSCF)with high electrical conductivity was used as the CCCL.A significant increase in the peak power density of the MT-SOFC to 1.2 W/cm^(2)at 850℃ was achieved using the proposed two-layer cathode.