Characterization of the 75% Gd0.8Sr0.2CoO3−δ/25% Ce0.9Gd0.1O2−δ composite cathode system for use in intermediate temperature solid oxide fuel cells

The composite cathode system is examined for suitability on a Ce_0.9Gd_0.1O_2−δ electrolyte based solid oxide fuel cell at intermediate temperatures (500–700 °C). The cathode is characterized for electronic conductivity and area specific charge transfer resistance. This cathode system is chosen for its excellent thermal expansion match to the electrolyte, its relatively high conductivity (115 S cm⁻¹ at 700 °C), and its low activation energy for oxygen reduction (99 kJ mol⁻¹). It is found that the decrease of sintering temperature of the composite cathode system produces a significant decrease in charge transfer resistances to as low as 0.25 Ω cm². The conductivity of the cathode systems is between 40 and 88 S cm⁻¹ for open porosities of 30–40%.     

Novel composite sorbent for resorption systems and for chemisorption air conditioners driven by low generation temperature

The utilization of a composite sorbent (NaBr and expanded graphite) in chemisorption air conditioning systems driven by low-grade heat source, and in resorption systems with simultaneous heating and cooling effects was experimentally investigated using bench-scale prototypes. The mass of ammonia desorbed and adsorbed was measured, and used to calculate the specific cooling capacity. The sorbent produced 219 kJ kg⁻¹ of cooling at 5 °C and 510 kJ kg⁻¹ at 15 °C, when the heat source temperature was 65 °C and the heat sink temperature was 30 °C. The air conditioning system mean specific cooling power (SCP), and mean coefficient of performance (COP) were calculated based on the desorbed and adsorbed masses, and on the variation of temperature in the reactors. For the same heat source and heat sink temperatures mentioned above, the air conditioning system had a SCP of 129 ± 7 W kg⁻¹ and a COP of 0.46 ± 0.01, when cooling occurred at 15 °C. Regarding the utilization of the composite sorbent in resorption machines, the prototype was tested for production of cooling/heating at −5/50 °C, and at 10/70 °C. In the former condition, the COP was only 0.02, but in the latter condition, there was a tenfold increase in the COP, and the combined coefficient of performance and amplification reached 1.11, which indicates the energy saving potential of resorption systems using the studied sorbent.     

Electrochemical impedance studies of electrooxidation of methanol and formic acid on Pt/C catalyst in acid medium

Cyclic voltammetry (CV), amperometric i − t experiments, and electrochemical impedance spectroscopy (EIS) measurements were carried out by using glassy carbon disk electrode covered with the Pt/C catalyst powder in solutions of 0.5 mol L⁻¹ H₂SO₄ containing 0.5 mol L⁻¹ CH₃OH and 0.5 mol L⁻¹ H₂SO₄ containing 0.5 mol L⁻¹ HCOOH at 25 °C, respectively. Electrochemical measurements show that the activity of Pt/C for formic acid electrooxidation is prominently higher than for methanol electrooxidation. EIS information also discloses that the electrooxidation of methanol and formic acid on the Pt/C catalyst at various polarization potentials show different impedance behaviors. The mechanisms and the rate-determining steps of formic acid electrooxidation are also changed with the increase of the potential. Simultaneously, the effects of the electrode potentials on the impedance patterns were revealed.     

Pyrolysis kinetics behaviour and thermal pyrolysis of Samanea saman seeds towards the production of renewable fuel

The present study addresses pyrolysis behaviour and potential of Samanea saman seeds (SS) towards its bioenergy potential using thermogravimetric analyzer and in a cylindrical pyrolyzer (semi-batch reactor). Pyrolysis kinetic behaviour of biomass was carried out using Kissinger, Distributed Activation Energy Model (DAEM) and Miura-Maki-Integral method (MMI) while thermal pyrolysis was carried out in a cylindrical shaped semi-batch reactor. Kinetic results confirmed that the average activation energy was found 118.24 kJ mol⁻¹, 168.70 kJ mol⁻¹, and 97.87 kJ mol⁻¹ for Kissinger, DAEM, and MMI model respectively. Further, thermal pyrolysis of SS biomass yielded 44.20 wt% yield of pyrolytic liquid (31.20 wt% pyrolytic oil/organic oil and 13 wt% aqueous fraction). Characterization results of pyrolytic oil showed the presence of higher viscosity (86.01 cSt), higher oxygen content (33.11%), and lower ash content (0.46 wt%) and gross heating value. FTIR analysis confirmed mainly the presence of aromatics, acid, alkene, water, and protein impurities. Gas Chromatography (GC) results declared, an increase in hydrocarbon and hydrogen gas with an increase in temperature while reduced the generation of CO and CO₂. Further, GC-MS analysis of pyrolytic oil revealed the presence of higher acids (19.46%), phenols (11.01%) ethers (11.12%) and ester (7.33%) which is a potent source of oxygenated compounds. Characterization results of biochar showed the presence of higher gross heating value (23.14 MJ kg), carbon content (62.66%), volatile matter (34.15%) and lower moisture (5.14%) and BET surface area (8.20 m² g⁻¹). Combining these results, it can be suggested that SS biomass has the potential to produce renewable fuel and chemicals, while biochar can be used for various applications.     

Promoting effect of biomass ash additives on high-temperature gasification of petroleum coke: Reactivity and kinetic analysis

The effect of biomass ash (rice straw ash (RSA) and cotton straw ash (CSA)) on the gasification reactivity and the evolution of physicochemical structure of petcoke char was investigated. The catalytic effect of CSA was significantly higher than that of RSA, and the catalytic effect of biomass ash was enhanced at lower gasification temperature and for higher blending ratio of biomass ash. The promoting effect of biomass ash was related to the increase of active AAEM content, the decrease of order degree of carbon structure and the development of surface structure in char gasification after biomass ash addition, which was more significant for CSA, at lower temperature and for higher blending ratio. Moreover, the shrinking core model was suitable for char gasification, and the additions of RSA and CSA reduced the activation energy of petcoke char gasification from 199.84 kJ mol⁻¹ to 159.85 kJ mol⁻¹ and 62.75 kJ mol⁻¹, respectively.     

Performance analysis of non-isothermal solar reactors for methanol decomposition

A procedure for analyzing the performance of non-isothermal solar reactors for methanol decomposition was developed, based on a model of thermal loss from direct steam generation collector and a comprehensive kinetic model of methanol decomposition employing BASF K3-110 catalyst. It was found that catalytic bed temperature tends towards a certain value, which depends on the chemical reaction type, radiation intensity and collector structure mainly. For a beam incidence angle of 0°, system efficiency increases from 56% at a radiation intensity of 400 W m⁻² to almost 58% at a radiation intensity of 1000 W m⁻². For a radiation intensity of 400 W m⁻², beam incidence angle of 20°, absorber length of 10 m, feed temperature of 373 K and ratio of reaction section of 0.9, the mole flow rate of feed in the range of 0.21–0.23 mol s⁻¹ results in a maximum quantity of reacted methanol of 0.146 mol s⁻¹, while a mole flow rate of feed of 0.15 mol s⁻¹ leads to a maximum system efficiency of 54.2%. The research indicates that the pre-heating section should be as short as possible for effective use of solar energy.     

Efficient generation of hydrogen from biomass without carbon monoxide at room temperature – Formaldehyde to hydrogen catalyzed by Ag nanocrystals

In this paper, we present a new route for hydrogen generation from biomass at room temperature without any carbon monoxide over nano-metal-catalysts. It has been found that the Ag nanocrystals are highly efficient and stable catalysts for the CO-free hydrogen production from formaldehyde (HCHO), a model compound of biomass, at room temperature and at atmospheric pressure. By optimizing the structure and component of catalysts, reaction parameters such as temperature, catalyst amounts, oxygen, formaldehyde concentrations, and NaOH concentrations, the hydrogen generation rate has been maintained for hours without any decay. Furthermore, the apparent activation energy of the Ag catalyzed hydrogen production reaction is determined to be 11.8 kJ mol⁻¹, which was much lower than that of the literature results (65 kJ mol⁻¹) without catalyst. Because of its high hydrogen generation rate, hydrogen generation efficiency, lower activation energy, and the low cost, we speculate that this novel Ag catalyst based hydrogen generation reaction should be a promising candidate for providing hydrogen in PEMFCs at room temperature.     

Hydrogen desorption properties of Mg thin films at room temperature

Pd–Mg–Pd thin films prepared by magnetron sputtering could absorb hydrogen entirely at room temperature and dehydrogenate completely and rapidly in ambient air. Our investigations of the structural, optical and electrical properties gave a detailed insight into the desorption mechanism. The overall activation energy and the hydrogen diffusion coefficient were deduced to be 48 kJ mol⁻¹ and 8.0 × 10⁻¹⁵ cm² s⁻¹ based on optical and electrochemical measurements, respectively. The desorption process followed the nucleation and growth mechanism by modeling and simulating the resistance data. The small activation energy and remarkable diffusion kinetics highlighted the applicability as on-board hydrogen storage systems.     

Preparation of sulfonated poly(ether ether ketone)s containing amino groups/epoxy resin composite membranes and their in situ crosslinking for application in fuel cells

A series of amino-containing sulfonated poly(aryl ether ketone)/4,4′-diglycidyl(biphenyl) epoxy resin (DGBP) composite membranes for proton exchange membranes fuel cells (PEMFCs) are prepared by solution blending and casting. The reaction kinetics and the effects of introduction of DGBP content on the properties of the composite membranes are thoroughly investigated. The crosslinked composite membranes after treatment at either 120 °C or 200 °C have improved oxidative and dimensional stability than those without crosslinking. Despite the fact that crosslinked membranes generally have lower proton conductivity in comparison with the original ones, the proton conductivities of the membranes treated at 120 °C are above 2.22 × 10⁻² S cm⁻¹ at room temperature and 9.42 × 10⁻² S cm⁻¹ at 100 °C. Even for the samples treated at 200 °C, their proton conductivities are still higher than 1.26 × 10⁻² S cm⁻¹ at room temperature and higher than 8.67 × 10⁻² S cm⁻¹ at 100 °C, which are well satisfied with elementary requirement of fuel cells. In addition, all the evaluated membranes have low methanol permeability. For example, the methanol permeability of AP6FSPEEK/DGBP1 cured at 200 °C is 0.33 × 10⁻⁶ cm² s⁻¹, which is an order magnitude lower than Nafion 117. Therefore, these novel crosslinked composite membranes could be potential usage in fuel cells.     

New proton conducting polymer blends and their fuel cell performance

Novel polymer blends based on aromatic polyethers with pyridine units have been prepared for their use as electrolytes after being doped with phosphoric acid for high temperature PEM fuel cells. They exhibit very good film-forming properties, mechanical integrity, high modulus up to 230 °C, high glass transition temperatures (up to 260 °C) and high thermal stability up to 400 °C. In addition to the above required properties, these novel materials show high oxidative stability and acid doping ability, enabling proton conductivity in the range of 10⁻² S cm⁻¹ at 130 °C. The preparation and fuel cell testing of membrane electrode assemblies, demonstrated very promising performance, and an initial study has shown the positive effect of humidity on the measured conductivity.     

Optimization and microbial community analysis for production of biohydrogen from palm oil mill effluent by thermophilic fermentative process

The optimum values of hydraulic retention time (HRT) and organic loading rate (OLR) of an anaerobic sequencing batch reactor (ASBR) for biohydrogen production from palm oil mill effluent (POME) under thermophilic conditions (60 °C) were investigated in order to achieve the maximum process stability. Microbial community structure dynamics in the ASBR was studied by denaturing gradient gel electrophoresis (DGGE) aiming at improved insight into the hydrogen fermentation microorganisms. The optimum values of 2-d HRT with an OLR of 60 gCOD l⁻¹ d⁻¹ gave a maximum hydrogen yield of 0.27 l H₂ g COD⁻¹ with a volumetric hydrogen production rate of 9.1 l H₂ l⁻¹ d⁻¹ (16.9 mmol l⁻¹ h⁻¹). The hydrogen content, total carbohydrate consumption, COD (chemical oxygen demand) removal and suspended solids removal were 55 ± 3.5%, 92 ± 3%, 57 ± 2.5% and 78 ± 2%, respectively. Acetic acid and butyric acid were the major soluble end-products. The microbial community structure was strongly dependent on the HRT and OLR. DGGE profiling illustrated that Thermoanaerobacterium spp., such as Thermoanaerobacterium thermosaccharolyticum and Thermoanaerobacterium bryantii, were dominant and probably played an important role in hydrogen production under the optimum conditions. The shift in the microbial community from a dominance of T. thermosaccharolyticum to a community where also Caloramator proteoclasticus constituted a major component occurred at suboptimal HRT (1 d) and OLR (80 gCOD l⁻¹ d⁻¹) conditions. The results showed that the hydrogen production performance was closely correlated with the bacterial community structure. This is the first report of a successful ASBR operation achieving a high hydrogen production rate from real wastewater (POME).     

ZnO-doped BaZr0.85Y0.15O3−δ proton-conducting electrolytes: Characterization and fabrication of thin films

ZnO-doped BaZr_0.85Y_0.15O_3−δ perovskite oxide sintered at 1500 °C has bulk conductivity of the order of 10⁻² S cm⁻¹ above 650 °C, which makes it an attractive proton-conducting electrolyte for intermediate-temperature solid oxide fuel cells. The structure, morphology and electrical conductivity of the electrolyte vary with sintering temperature. Optimal electrochemical performance is achieved when the sintering temperature is about 1500 °C. Cathode-supported electrolyte assemblies were prepared using spin coating technique. Thin film electrolytes were shown to be dense using SEM and EDX analyses.     

Experimentation of a solar adsorption refrigerator in Morocco

For countries with a high potential of solar energy, producing cold using solar energy is a promising way to sustainable development since the energy used is free and not harmful for the environment.This work proposes a solar adsorption refrigerator using the pair activated carbon–methanol, which has been totally built and is under experimental tests in the solar laboratory of the Faculty of Sciences of Rabat, the capital of Morocco with Mediterranean climate.The solar adsorption refrigerator is mainly composed of a collector containing the adsorbent, an evaporator and a condenser. The results show that the refrigerator gives good performance in Rabat. The unit produces cold even in rainy and cloudy days and the temperatures achieved by the unit can be less than −11 °C for days with a very high irradiation. The solar coefficient of performance (COP) (cooling energy/solar energy) ranges between 5% and 8% for an irradiation between 12,000 and 28,000 kJ m⁻² and a daily mean ambient temperature around 20 °C.     

Carbon-coated graphite for anode of lithium ion rechargeable batteries: Graphite substrates for carbon coating

Anode performance in lithium ion rechargeable batteries (LIBs) was studied on four kinds of graphite powders, including synthetic graphite. Carbon-coated synthetic graphite gave a smaller irreversible capacity of about 20 mAh g⁻¹ and a better cyclic performance in an electrolyte solution of EC/DMC than natural graphite, though its discharge capacity of about 300 mAh g⁻¹ is a little smaller than natural graphite. Even in a PC-containing solution as EC/PC = 3/1, carbon-coated synthetic graphite had almost the same anode performance as in the solution without PC. Carbon coating of above 5 mass% on graphite particles was found to be effective to improve the anode performance at a low temperature of −5 °C, high retention in discharge capacity of about 90% being obtained. On both natural and synthetic graphite powders, carbon coating by the amount of 3–10 mass% at a temperature of 700–1000 °C was found to be optimum for the improvement of anode performance in LIBs, to have a lower irreversible capacity and higher retention in discharge capacity at −5 °C than without carbon coating.     

Structural, thermal and electrochemical properties of layered perovskite SmBaCo2O5+d, a potential cathode material for intermediate-temperature solid oxide fuel cells

The synthesis, conductivity properties, area specific resistance (ASR) and thermal expansion behaviour of the layered perovskite SmBaCo₂O_5+d (SBCO) are investigated for use as a cathode material for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The SBCO is prepared and shows the expected orthorhombic pattern. The electrical conductivity of SBCO exhibits a metal–insulator transition at about 200 °C. The maximum conductivity is 570 S cm⁻¹ at 200 °C and its value is higher than 170 S cm⁻¹ over the whole temperature range investigated. Under variable oxygen partial pressure SBCO is found to be a p-type conductor. The ASR of a composite cathode (50 wt% SBCO and 50 wt% Ce_0.9Gd_0.1O_2−d, SBCO:50) on a Ce_0.9Gd_0.1O_2−d (CGO91) electrolyte is 0.05 Ω cm² at 700 °C. An abrupt increase in thermal expansion is observed in the vicinity of 320 °C and is ascribed to the generation of oxygen vacancies. The coefficients of thermal expansion (CTE) of SBCO is 19.7 and 20.0 × 10⁻⁶ K⁻¹ at 600 and 700 °C, respectively. By contrast, CTE values for SBCO:50 are 12.3, 12.5 and 12.7 × 10⁻⁶ K⁻¹ at 500, 600 and 700 °C, that is, very similar to the value of the CGO91 electrolyte.     

New iodide-based molten salt systems for high temperature molten salt batteries

Novel multi-component molten salt systems containing iodides, LiF–LiBr–LiI, LiF–NaBr–LiI, and LiF–LiCl–LiBr–LiI, were investigated for use as electrolytes in high temperature molten salt batteries to improve the discharge rate-capability. The iodide-based molten salts showed higher ionic conductivity (3 S cm⁻¹ at 500 °C) than conventional LiCl–KCl, and had low enough melting points (below 400 °C) that can be used in practical high temperature molten salt batteries. The iodide-based salts showed instability at temperatures higher than 280 °C in dried air. The decomposition mechanism of iodide-based molten salts was discussed, and it was found that elimination of oxygen from the environment is effective to stabilize the iodide-based molten salts at high temperatures.     

Ruthenium nanoparticles supported in the network of HES-p(AMPS) IPN hydrogel as efficient catalyst for hydrogen production from the hydrolysis of ethylenediamine bisborane

In this study, Ru(0) nanoparticles supported in 2-hydroxyethyl starch-p-(2-Acrylamido-2-methyl-1-propanesulfonic acid) interpenetrating polymeric network (HES-p(AMPS) IPN) were synthesized as hydrogel networks containing hydroxyethyl starch, which is a natural polymer with oxygen donor atoms. The structure and morphology of the prepared HES-p(AMPS) IPN hydrogel and Ru@HES-p(AMPS) IPN catalyst were characterized using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), X-ray diffraction (XRD), and transmission electron microscope (TEM). Ru@HES-p(AMPS) IPN was used as catalyst for hydrogen production from the hydrolysis of ethylenediamine bisborane (EDAB). The activation parameters for the hydrolysis reaction of EDAB catalyzed by Ru@HES-p(AMPS) IPN were calculated as E_a = 38.92 kJ mol⁻¹, ΔH^# = 36.28 kJ mol⁻¹, and ΔS^# = −111.85 J mol⁻¹ K⁻¹, respectively. The TOF for the Ru@HES-p(AMPS) IPN catalyst was 2.253 mol H₂ (mol Ru(0) min)⁻¹. It was determined that Ru@HES-p(AMPS) IPN, a reusable catalyst, still had 81.5% catalytic activity after the 5th use.     

Spatial assessment of the bioenergy potential of forest residues in the western province of Spain, Caceres

The present work is mainly devoted to provide a rigorous analysis on the quantification, the mapping and the management of the bioenergy potential of forest residues from the most representative forestry species of the west-central region of Spain (Cáceres).An appropriate methodological approach for the estimate of potential biomass and potential bioenergy as well as the use of GIS for data process are both crucial for the design of thermal plants and for the accurate estimate of biomass collection and transportation costs, according to the scale economy of the plant.The total forest residues in the province of Cáceres are estimated as 463 000 t y⁻¹. The availability of such major biomass potential for energy production is strongly conditioned to the inherent difficulties during the extraction process. This way, an energy potential of 139 000 toe y⁻¹ would be achieved if the above-mentioned biomass collection rate is assumed.The method to optimise the search for suitable locations for thermal plants as well as for biomass extraction/collection areas, based on the combined use of GIS and spatial analysis techniques, is also described.     

New hybrid inorganic–organic polymer electrolytes based on Zr(O(CH2)3CH3)4, glycerol and EMIm-TFSI ionic liquid

This report presents detailed studies on the elemental analysis, vibrational spectroscopy, thermal stability and electrical spectroscopy of two new hybrid inorganic–organic polymers which have been synthesised by a sol–gel method using glycerol and zirconium(IV)butoxide as precursors. These materials have been doped by means of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIm-TFSI) ionic liquid (IL), which is insoluble in water. The elemental composition of the obtained polymers [Zr(C₆O₅H₁₁)] (1) and [Zr(C₁₁O₄H₃₁)] (2) has been determined by CHN analysis and by ICP-AES measurements. FT-IR and FT-Raman spectroscopy investigations have been performed to study the molecular structure of the polymers and the interactions of EMIm-TFSI with the host networks. Differential scanning calorimetry measurements show the presence of at least one glass transition temperature (T_g) in both 1 and 2 materials. The broadband dielectric spectroscopic measurements have been carried out between 10⁻² Hz to 10 MHz from −100 °C to 100 °C with a 5 °C step. The conductivities of the polymers 1 and 2 have been found to be in the order of 10⁻⁸ to 10⁻¹¹ S cm⁻¹ at 25 °C, so they can be defined as dielectric materials. After doping 2 with EMIm-TFSI, the conductivity at 25 °C of the obtained complex [Zr(C₁₁O₄H₃₁)]₁₅/(EMIm-TFSI) (2′) increased three orders of magnitude resulting ca. 10⁻⁵ S cm⁻¹. The permittivity spectra revealed two relaxation bands which were attributed to the α relaxation modes of the polymer networks.     

Biohydrogen production from pig slurry in a CSTR reactor system with mixed cultures under hyper-thermophilic temperature (70 °C)

A continuous stirred tank reactor (CSTR) (750 cm³ working volume) was operated with pig slurry under hyper-thermophilic (70 °C) temperature for hydrogen production. The hydraulic retention time (HRT) was 24 h and the organic loading rate was 24.9 g d⁻¹ of volatile solid (VS). The inoculum used in the hyper-thermophilic reactor was sludge obtained from a mesophilic methanogenic reactor. The continuous feeding with active biomass (inoculum) from the mesophilic methanogenic reactor was necessary in order to achieve hydrogen production. The hyper-thermophilic reactor started to produce hydrogen after a short adapted period of 4 days. During the steady state period the mean hydrogen yield was 3.65 cm³ g⁻¹ of volatile solid added. The high operation temperature of the reactor enhanced the hydrolytic activity in pig slurry and increased the volatile fatty acids (VFA) production. The short HRT (24 h) and the hyper-thermophilic temperature applied in the reactor were enough to prevent methanogenesis. No pre-treatment methods or other control methods for preventing methanogenesis were necessary. Hyper-thermophilic hydrogen production was demonstrated for the first time in a CSTR system, fed with pig slurry, using mixed culture. The results indicate that this system is a promising one for biohydrogen production from pig slurry.