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Fire extinguishing technologies of fine water mist containing additives have good application prospects. Additives that are efficient, nontoxic, nonpolluting, widely used, economical and reliable provide a reference for the application and promotion of fine water mist fire extinguishing systems containing alkali metal salts. In this paper, six potential alkali metal salt additives were selected: potassium carbonate (K 2 CO 3), sodium carbonate (Na 2 CO 3), potassium oxalate (K 2 C 2 O 4 ·H 2 O), potassium acetate (CH 3 COOK), potassium chloride (KCl), and potassium bicarbonate (KHCO 3); these additives were delivered into the fires as mists of their solutions at certain concentrations, the extinguishing time was recorded, and the minimum fire extinguishing concentration (MEC) of fine water mist containing alkali metal salt was tested by using a cup burner experimental apparatus. In addition, different types of alkali metal salts were compared to determine the anions and cations with better fire suppression performance levels. The suppression efficiencies of different ratios of additive packages for hydrogen-doped natural gas diffusion flames were studied to determine a specific ratio of additive packages. Based on the results of the experiment, in contrast to the pure water mist, the suppression efficiency of alkali metal salt greatly improved. The cation extinguishing ability was K+>Na+, and CO 3 2- and CH 3 COO− were better than other anions in alkali metal salts. An efficient compound additive was identified as 1.5% K 2 CO 3 + 0.5% CH 3 COOK. With increasing hydrogen addition, the MEC of fine water mist with additives increased. • The addition of alkali metal salts improved the suppression efficiency. • With the increase of H 2 addition, the MEC of fine water mist with additive increased. • An efficient compound additive was identified as: 1.5% K 2 CO 3 + 0.5% CH 3 COOK. [ABSTRACT FROM AUTHOR]

Aqueous formate/bicarbonate solutions are gaining special attention as a promising system for intrinsically safe hydrogen storage. In the last years, a growing number of papers are investigating catalytic systems to enhance salts interconversion at near-ambient conditions. In this work, we present detailed thermodynamic calculations to clarify the maximum storage capacity of such a system. The model is validated against experimental results reported in the literature and the influence of operating conditions is addressed. Based on the results, the performances of the most promising configurations are simulated for experimental benchmarking and future technological development. Thermodynamic limitations show that maximum volumetric density is lower than traditional physical-based H 2 storage, but with considerable advantage from a safety point of view. [Display omitted] • Formate/bicarbonate thermodynamics for H 2 storage was investigated. • Configurations were studied for experimental benchmarking and future applications. • Maximum achievable volumetric density is 1/5 to 1/2 of traditional H 2 storage. • Reduced volumetric density is offset by substantially reduced risk. [ABSTRACT FROM AUTHOR]

Carbonate/oxide composites are very promising electrolyte materials in hybrid fuel cells which could operate at lower temperature than the usual Molten Carbonate Fuel Cells (MCFC) or Solid Oxide Fuel Cells (SOFC), presenting 0.1 S cm −1 at 600 °C. This paper shows some significant and/or unexpected experimental data obtained by impedance spectroscopy, related to the impact of the carbonate/oxide ratios and the heating and cooling cycles in reducing atmospheres on the electrical behaviour of the composites. Based on this peculiar experimental behaviour, combined DFT calculations are selected for acquiring a deeper understanding of the transport mechanisms in such materials. A modelling strategy, in parallel with experimental results, is developed in the present paper. [ABSTRACT FROM AUTHOR]

High-pressure hydrogen-rich gas producing experiments from various alcohol/water/metal-powder mixtures at low processing temperatures from 473 to 723 K are carried out in a prototype airtight apparatus possessing a withstand pressure of 15 MPa in the aim of technologizing an incidentally emerged high-pressure hydrogen-rich gas production from a methanol/water/aluminum-powder mixture at 723 K. Methanol/water due to a proven track record and ethanol/water in order to make an allowance for replacing the reagent to commercially-available potable alcohols are selected as main hydrogen sources. As tested metal-powders, aluminum, cobalt, iron, magnesium and nickel are chosen, taking their ready-availabilities and costs into consideration. Among tested metal-powders, aluminum and cobalt are found optimal adding metals for the high-pressure hydrogen-rich gas productions from 60.0 wt% methanol/water and ethanol/water solutions, respectively. From 60.0 wt% methanol/water and Al-powder mixture at 723 K, pure-hydrogen with 10.0 MPa is produced at a great hydrogen producing rate of 24.9 L N /(dm2min). All carbons discharged from methanol are fixed as a wide variety of solid higher hydrocarbons and organic liquid residues of benzyl alcohol and toluene. Almost all oxygens from methanol/water solution are fixed as aluminum-compounds of aluminum oxide hydroxide and aluminum hydroxide. From 60.0 wt% ethanol/water and Co-powder mixture, pure-hydrogen with pretty high pressure over 15 MPa can be produced at 723 K with simultaneous fixations of all the carbons and oxygens from the main hydrogen source as solid/liquid residues of wide variety of solid higher hydrocarbons, benzyl alcohol, toluene, cobalt oxide, cobalt hydroxide, tricobalt tetroxide and cobalt carbonate. Responding to the outcome from 60.0 wt% ethanol/water and Co-powder mixture, a certain rice-wine having an alcohol degree 60 with Co-powder at 723 K is experimented, and provides high-pressure hydrogen-rich gas with hydrogen concentration of 80 % and hydrogen partial pressure of around 8 MPa. All the produced hydrogen-rich gases are confirmed to keep a full declared potential in polymer electrolyte fuel cell for over 24 h without any exceptions. These findings speak by themselves that this developing high-pressure hydrogen-rich gas (pure-hydrogen) direct producing method is surely approaching a self-operating dispersed hydrogen producing appliance (i.e. a part of a dispersion type power source) anywhere whole the world. And, this method still leaves unlimited room for far higher pure-hydrogen pressures and hydrogen producing rates by slight changing the operating conditions, and its applicable fields are broadening for eternity. Finally, some recommended future strategies to improve this method so as to supply complete solutions to any global-scale issues are also proposed in every part through this paper. • Pure-hydrogen with 10.0 MPa is produced from methanol/water/Al-powder at 723 K. • Maximum pure-hydrogen producing rate is 24.9 L N /(dm2min). • Pure-hydrogen with above 15 MPa is produced from ethanol/water/Co-powder at 723 K. • Hydrogen-rich gas with around 8 MPa is produced from rice-wine/Co-powder at 723 K. • All produced hydrogen-rich gases keep a full potential in PEFC for over 24 h. [ABSTRACT FROM AUTHOR]

Molten carbonate fuel cells (MCFCs) are promising high temperature power generating devices. However, unlike solid oxide fuel cells (SOFCs) they utilize a liquid electrolyte which must be immobilized in a porous matrix. In this paper, a slurry composition for lithium aluminate ( γ -LiAlO 2 ) matrix was developed and green matrices were subsequently formed by the tape casting method. In order to achieve the desired structure of the matrix (pore size, porosity) γ -LiAlO 2 powder was milled in a planetary ball mill for 18 h with a solvent, dispersant and defoamer. After this step, other ingredients were added, including a binder and plasticizer to obtain optimal rheology of the slurry. Cell tests confirmed optimal performance of the matrix compared to the third party reference γ -LiAlO 2 matrices. Burned out matrix was characterized by scanning electron microscopy (SEM) and laser diffraction in order to determine the γ -LiAlO 2 powder particle size and morphology. The results show that high-energy milling enabled a fine pore structure and high specific surface area of the matrix to be obtained in a relatively short time, compared to conventional fabrication routes. The matrix structure obtained within this study is suitable for high performance operation of MCFC. [ABSTRACT FROM AUTHOR]

The electrochemical transformation of CO 2 into more valuable chemicals such as CO offers great interest in the energetic field. In this paper, the feasibility of this valorisation process is investigated by cyclic voltammetry in different binary molten carbonates: Li 2 CO 3 Na 2 CO 3 (52:48 mol. %), Li 2 CO 3 K 2 CO 3 (62:38 mol. %) and Na 2 CO 3 K 2 CO 3 (56:44 mol. %) and in a ternary eutectic: Li 2 CO 3 Na 2 CO 3 K 2 CO 3 (43.5:31.5:25 mol. %). The eutectic nature, the oxoacidity, temperature and scanning conditions on the reduction and oxidation peaks is thoroughly analysed. The reduction peak related to CO 2 reduction into CO is diffusion-controlled and slow quasi-reversible; in specific experimental conditions, it is split into two peaks of similar intensity. Re-oxidation peaks are most probably due to dissolved and adsorbed CO. Based on our experimental investigation under varied conditions such as molten salt composition, oxoacidity, temperature of the system and thermodynamic predictions regarding carbon presence, two mechanistic schemes are proposed, involving gaseous, dissolved and adsorbed species. [ABSTRACT FROM AUTHOR]

Novel composite materials based on La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 2.85 (LSGM) and a binary eutectic carbonates (52 mol% Li 2 CO 3 :48 mol% Na 2 CO 3 ) are potential electrolytes for low-temperature solid oxide fuel cells (LTSOFCs) operating at 400–600 °C. However, thermal stability of the LSGM–(Li/Na) 2 CO 3 composites remains in doubt due to the molten state of the carbonates at elevated temperature. In this paper, XRD, SEM, TGA and EIS were employed for thermal ageing and cycling studies of the LSGM–(Li/Na) 2 CO 3 composites. XRD and SEM results showed that ageing induced a slight effect on the structure and morphology of the composites. TGA and EIS results indicated that the composites had a good stability during cycling. The LSGM–20 wt% (Li/Na) 2 CO 3 sample showed a relatively stable conductivity (7–9 × 10 −2 S cm −1 ) during a 650 h measurement under air at 600 °C. Single cell based on the composite electrolytes was reported for the first time, a maximum power density of 617 W cm −2 and the open circuit voltage (OCV) of 1.01 V were achieved at 600 °C for the composite containing 20 wt% carbonates. The notable thermal stability together with fairly high performance emphasize the promise of LSGM–(Li/Na) 2 CO 3 composite electrolytes for long-term LTSOFCs. [ABSTRACT FROM AUTHOR]

In this paper we synthesized a crystalline Ag-C i oxygen-evolution catalyst with an entirely new composition and structure in situ in a carbonate solution (pH = 8.3) with Ag+ at 70 °C. We studied the factors that influenced the synthesis of the oxygen-evolution catalyst (electrolyte environment temperature, silver ion concentration, concentration of carbonates) under mild conditions. The structure, morphology, composition, and catalytic activity of Ag-C i catalyst were analyzed using techniques such as X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and electrochemical measurements. Our results showed that the diffraction peaks of the Ag-C i catalysts synthesized at 70 °C were consistent with the AgO phase and that the catalytic composition of the Ag-C i catalyst was the AgⅠO/AgⅡO redox couple. The oxygen-evolution rate of the catalyst synthesized in a carbonate solution (pH = 8.3) at 70 °C was 50 times higher than that synthesized at 5 °C (18.3 μmol h−1); additionally, its oxygen evolution overpotential decreased to 246.7 mV. The electrolyte solution and Ag+ ion concentration greatly impacted the catalytic activity of the Ag-C i catalyst for water splitting. [ABSTRACT FROM AUTHOR]

Abstract: NiO-Samaria-Doped-Ceria (NiO-SDC) composite powders was synthesized by a traditional mechanical mixing process and tested as anode material for Direct Carbon Fuel Cell (DCFC), which uses almond shell biochar as fuel and molten carbonate-doped ceria composite as electrolyte. A three-layer pellet cell, viz. cathode (Lithiated NiO-SDC), composite electrolyte and anode (NiO-SDC) is fabricated by a die-pressing, screen printing and sintering method. In Part I, a bi-layer DCFC pellet powered by almond shell biochar was tested and demonstrated a good potential. In this paper, we report an improvement in the cell stability and performance by adding the (NiO-SDC) anode layer to the bi-layer pellet containing only cathode and electrolyte. The peak power density of the three-layer pellet cell at 700 °C increases to reach 150 mW cm−2 instead of 127 mW cm−2 while, the stability period is ameliorated to be around 130 min. The results indicated that this porous anode material is promising as anode for DCFCs. The DCFC single cells experiments demonstrated that the anode polarization is dominating the total cell polarization. Therefore, improved power output could be achieved with an improved anode. [Copyright &y& Elsevier]

Abstract: Composite materials based on gadolinia-doped ceria (GDC) and alkali carbonates (Li2CO3-K2CO3 or Li2CO3-Na2CO3) are potential electrolytes for low temperature solid oxide fuel cell applications (LTSOFC). This paper completes a first one dedicated to the thermal, structural and morphological study of such compounds; it is fully focussed on their electrical/electrochemical properties in different conditions, temperature, composition and gaseous atmosphere (oxidative or reductive). The influence of the gaseous composition on the Arrhenius conductivity plots is evidenced, in particular under hydrogen atmosphere. Finally, electrical conductivity determined by impedance spectroscopy is presented as a function of time to highlight the stability of such composites over 6000 h. First results on single cells showed performance at 600 °C of 60 mW cm−2. [Copyright &y& Elsevier]

Abstract: Composite materials with alkali carbonate and magnesia have been examined for high-temperature thermal storage in solar tubular reformers. The concept of a double-walled reactor tube involves packing a molten-salt/ceramic composite material into the annular region between internal catalyst tube and exterior solar-absorber wall. In this paper, the shape and interior structure of the reactor tube are newly designed for use in solar cavity-type reformers using straight reactor tubes. Na2CO3, K2CO3, and Li2CO3 composite materials with magnesia were tested as thermal storage media for CO2 reforming of methane during cooling mode of the reactor tube at a laboratory scale. The efficiency of Na2CO3/MgO composite with various MgO contents was also estimated. Composite materials of Na2CO3 80–90wt% and MgO 20–10wt% were successfully delayed the cooling of the catalyst bed and sustained methane conversion at >90%. A solar cavity-type reformer consisting of multiple straight reactor tubes is expected to enable stable operation of the solar reforming process under fluctuating solar insolation during cloud passage. [Copyright &y& Elsevier]

Fuel cells are still a new technology, and the scientific community is in dire need for reliable data on their environmental performance. In this paper a multi-criteria life cycle assessment of a prototype molten carbonate fuel cells plant is performed; the results are subject to a systematic sensitivity analysis and compared to those for three natural gas turbine plants. Results indicate an overall good environmental performance, even when compared to modern gas turbines. Possible further improvements should focus on reducing the requirement for the employed metals (e.g. Ni, Cr), as well as increasing fuel cell life time and centralising the natural gas reforming phase. [Copyright &y& Elsevier]