A thermodynamically stable La2NiO4+δ/ Gd0.1Ce0.9O1.95 bilayer oxygen transport membrane in membrane-assisted water splitting for hydrogen production

A bilayer configuration of mixed ion-electron conducting La₂NiO_4+δ and oxygen-ion conducting Gd_0.1Ce_0.9O_1.95 (LNO/GDC10) was proposed for hydrogen production by water-splitting and its properties were measured as a function of temperature, reducing gas CO content and water vapor pressure during the hydrogen production by water-splitting. The hydrogen production flux increased with increasing water vapor pressure and oxygen chemical potential to a maximum of 0.12 cm³ (STP)/min-cm² with 23.25% CO/76.75% CO₂ (40 sccm)/balance He (60 sccm) gas mixture on the oxygen-permeate side and wet N₂ (pH₂O=0.49 atm) on the oxidizing side at 900 °C. The stability of the bilayer membrane was tested in a very low oxygen partial pressure (pO₂) on the oxygen-permeate side. The presence of GDC10 on the oxygen-permeate side of the bilayer prevented the direct exposure of LNO to very low pO₂ and thus protected it from decomposition, even at pO₂≈10^?15 atm.     

A wall-coated catalytic capillary microreactor for the direct formation of hydrogen peroxide

The direct formation of hydrogen peroxide from H₂ and O₂ was successfully carried out in a capillary microreactor at room temperature and atmospheric pressure. A key element in sustaining the activity of the catalyst is the incarceration of the palladium nanoparticles in a cross-linkable amphiphilic polystyrene-based polymer, prepared following the protocol of Kobayashi [R. Akiyama, S. Kobayashi, J. Am. Chem. Soc. 125 (2003) 3412–3413]. The immobilization effectively reduced the leaching of palladium under acidic conditions. Applying the catalyst as a coating on the inner walls of a capillary enabled the sustained production of 1.1% hydrogen peroxide over at least 11 days. The highest catalyst utilization in a 2 mm capillary reactor was 0.54 mol_H2O2/h g_Pd. When the inner diameter of the reactor capillary was reduced to 530 μm, the rate was enhanced fourfold to 2.28 mol_H2O2/h g_Pd corresponding to a turnover frequency of 0.067 s^?1.     

Heterogeneous membranes based on a composite of a hypercrosslinked microparticle adsorbent and polyimide binder

This paper deals with the preparation and characterization of heterogeneous membranes based on microparticle hypercrosslinked polymeric adsorbents with a polyimide binder. The polyimide based membrane extension is hindered by their low permeability. We enhanced the permeability of polyimide membranes by changed chemical structure and by adding of the new type fillers. Hypercrosslinked polystyrene microparticles of diameter 1–5 μm were prepared by SnCl₄-catalyzed Friedel–Crafts reaction of polystyrene with chloromethyl methyl ether in 1,2-dichlorethane solution. The precursor polyamic acid (PAA) was synthesized by the reaction of equimolar amounts of 4,4′-oxy(bis(phthalic anhydride)) (ODPA) and bis(4,4′-oxydianiline) (ODA) or 4,4′-[(1,4-phenylene)dipropane-2,2-diyl]dianiline (BIS P) in N-methylpyrrolidone (content 10 wt.%). A PAA solution in N-methylpyrrolidone with the adsorbent was spread onto a glass substrate and kept at 60–240 °C for 12 h. Heterogeneous membranes were characterized by thermal, mechanical and separation measurements. The permeability for membrane ODPA–BIS P filled with 10 wt.% of hypercrosslinked adsorbent was 3.5 × 10⁻¹¹ cm³(STP) cm cm⁻² s⁻¹ cmHg⁻¹ for nitrogen and 4 × 10⁻⁹ cm³(STP) cm cm⁻² s⁻¹ cmHg⁻¹ for hydrogen. The permeability of homogeneous polyimide membranes is up to one order of magnitude lower. The diffusion coefficient of heterogeneous membranes increased in the order CH₄ < N₂ < O₂ < CO₂ < H₂. The selectivity of hydrogen–nitrogen separation with the amount of adsorbent decreased from 164 to 69. The prepared membranes are intended for separation of gases and low organic molecules even at enhanced temperature. The present paper aims at giving information on the influence of hypercrosslinked adsorbents and polyimide binding materials on the gas separation properties of membranes.     

CO2-tolerant Ni-La5.5WO11.25-δ dual-phase membranes with enhanced H2 permeability

Enhancing the ambi-polar conductivity of the ceramic hydrogen permeable membrane by introducing an electron conductive metallic phase is quite effective, which is helpful for the hydrogen permeation flux improvement. To develop CO₂-tolerant hydrogen permeable membranes with better hydrogen permeability, Ni-La_5.5WO_11.25-δ (Ni-LWO) cermet membranes are fabricated. The alkaline earth metal-free ceramic LWO is used as the main proton-conductive phase and Ni is used as the main electron-conductive phase. The Ni-LWO membrane exhibits good chemical stability in CO₂-containing atmosphere since its hydrogen permeability maintains well in the measurement for about 180 h. Compared with the LWO ceramic membrane, the hydrogen permeability of the Ni-LWO membrane has been improved significantly. The Ni/LWO ratio has great impact on the performance of the cermet membrane. Meanwhile, among all the dual-phase Ni-LWO membranes with different Ni/LWO volume ratios, the membrane with 60 vol% Ni shows the highest hydrogen permeation flux of 0.18 ml min⁻¹ cm⁻² at 1000 °C when the feed gas contains 50% H₂.     

Preparation of dual-phase composite BaCe0.8Y0.2O3/Ce0.8Y0.2O2 and its application for hydrogen permeation

Dual-phase ceramic membranes composed of BaCe_0.8Y_0.2O₃ (BCY) and Ce_0.8Y_0.2O₂ (CYO) were successfully synthesized by solid state reaction method for hydrogen permeation. The influences of the BCY/CYO volume ratios on phase composition, microstructure, chemical stability and electrical property were investigated. The hydrogen permeation of the dual-phase composite was characterized as a function of temperature and feed side hydrogen partial pressure. The results showed that there was no reaction between the two constituent oxides observed under the preparation conditions. The dual-phase composite with different BCY/CYO volume ratios after sintering at 1550 °C exhibited dense structure, as well as good stability in 4% H₂/Ar, wet Ar and pure CO₂ atmosphere. The conductivity of the dual-phase composite increased with the content of CYO increasing and 30BCY–70CYO exhibited the highest total conductivity of 2.6×10⁻² S cm⁻¹ at 800 °C in 4% H₂/Ar. The hydrogen permeability of 30BCY–70CYO sample was improved as the temperature and the hydrogen partial pressure in feed gas increased. The hydrogen permeation flux of 1.7 μmol cm⁻² s⁻¹ was achieved at 850 °C.     

Chemical hydrogen storage and release properties using redox reaction over the Cu-added Fe/Ce/Zr mixed oxide medium

The chemical hydrogen storage (hydrogen reduction) and release (water-splitting oxidation) properties of the Cu-added Fe/Ce/Zr mixed oxide medium were investigated. The media with Cu content ranging from 0 to 5 wt% were prepared by a co-precipitation method using urea as a precipitant. The hydrogen reduction and the water-splitting oxidation on the medium were tested by temperature programmed reduction/oxidation (TPR/TPO) and repeated isothermal redox cycles at 550 °C for reduction and 350 °C for oxidation. The initial reduction rates and oxidation rates of the media increased with increasing the amount of the Cu additive. In addition, the reactivity of the medium for water-splitting oxidation was enhanced as the CeO₂/ZrO₂ ratio increased. Especially, the Fe-based mixed oxide medium with Cu/CeO₂/ZrO₂ contents of 3/30/10 wt% (Cu(3%)-Fe-CeO₂/ZrO₂(3/1)) showed superior performance in chemical hydrogen storage and release. As the results of isothermal redox cycles using the medium, the total amount of hydrogen evolved in water-splitting oxidation was maintained at ca. 8.5 mmol g^?1-medium (ca. 1.8 wt% hydrogen storage amounts on the basis of the total medium) over 15 repeated redox cycles.     

New morphological Ba0.5Sr0.5Co0.8Fe0.2O3−α hollow fibre membranes with high oxygen permeation fluxes

Perovskite Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3?α (BSCF) hollow fibre membranes were fabricated by a combined phase inversion and sintering technique. The membranes were characterised by XRD, SEM and tested for air separation. The membrane possesses a novel morphology consisting of one dense layer and one porous layer. Oxygen permeation fluxes through the obtained hollow fibre membranes were measured in the temperature range 650–950 °C using helium sweep gas rates from 50 to 200 mL min^?1. Experimental results indicated the oxygen permeation flux through the BSCF hollow fibre membrane sintered at 1050 °C was approximately 11.46 mL min^?1 cm^?2 at 950 °C when the helium sweep rate was kept at 200 mL min^?1. The BSCF hollow fibre membrane showed a stable oxygen permeation flux of 8.60 mL min^?1 cm^?2 over the investigated period of 120 h at 900 °C.     

Oxygen permeation properties of BSCF5582 tubular membrane fabricated by the slip casting method

BSCF5582 tubular oxygen separation membranes were prepared using the most cost effective slip casting techniques. The optimum slurry composition was identified and a dense, and crack free 60 mm long BSCF5582 tubular membrane being successfully prepared after the programmed sintering process. The effects of the feed flow rate and the sweeping flow rate on the oxygen permeation flux of the tubular BSCF5582 membrane were investigated. The oxygen permeation flux increased with an increase of the oxygen chemical potential gradient to a maximum of 42.5 cm³/min in an O₂/N₂ condition at 1223 K for the 1.5 mm thick, 60 mm long BSCF tube, a value which corresponds to 1.42 cm³/min cm². The ionic conductivity of the oxygen was successfully calculated in the dominant electron conducting regime. The ionic conductivity was found to increase with an increase of the temperature to 900 °C, indicating that it is a thermally activated process with an activation energy of 0.70 ± 0.1 eV in an air environment.     

High performance BaCe0.8Y0.2O3−a (BCY) hollow fibre membranes for hydrogen permeation

In this work, BaCe_0.8Y_0.2O_3−α (BCY) perovskite hollow fibre membranes were fabricated by a phase inversion and sintering method. BCY powder was prepared by the sol–gel technique using ethylenediaminetetraacetic acid (EDTA) and citric acid as the complexing agents. Gel calcination was carried out at high temperature to form the desired crystal structure. The qualified BCY hollow fibre membranes could not be achieved even the sintering was carried out at temperatures up to 1550^oC due to the poor densification behavior of the BCY material. The addition of sintering aid (1 wt% Co₂O₃) inside BCY powder as the membrane starting material significantly improved the densification process, leading to the formation of gas-tight BCY hollow fibres. The optimum sintering temperature of BCY hollow fibre membrane was 1400 °C to achieve the best mechanical strength. H₂ permeation through the BCY hollow fibre membranes was carried out between 700 and 1050 °C using 25% H₂–He mixture as feed gas and N₂ as sweep gas, respectively. For comparison purpose, the disk-shaped BCY membrane with a thickness of 1 mm was also prepared. The measured H₂ permeation flux through the BCY hollow fibres reached up to 0.38 mL cm⁻² min⁻¹ at 1050 °C strikingly contrasting to the low values of less than 0.01 mL cm⁻² min⁻¹ from the disk-shaped membrane. After the permeation test, the microstructure of BCY hollow fibre membrane was still maintained well without signals of membrane disintegration or peeling off.     

Preparation and characterization of BaCe0.95Tb0.05O3−α hollow fibre membranes for hydrogen permeation

BaCe_0.95Tb_0.05O_3?α (BCTb) perovskite hollow fibre membranes were fabricated by spinning the slurry mixture containing 66.67 wt% BCTb powder, 6.67 wt% polyethersulphone (PESf) and 26.67 wt% N-methyl-2-pyrrolidone (NMP) followed by sintering at elevated temperatures. The influence of sintering temperature on the membrane properties was investigated in terms of crystal phase, morphology, porosity and mechanical strength. In order to obtain gas-tight hollow fibres with sufficient mechanical strength, the sintering temperature should be controlled between 1350 and 1450 °C. Hydrogen permeation through the BCTb hollow fibre membranes was carried out between 700 and 1000 °C using 50% H₂–He mixture as feed on the shell side and N₂ as sweep gas in the fibre lumen. The measured hydrogen permeation flux through the BCTb hollow fibre membranes reached up to 0.422 μmol cm^?2 s^?1 at 1000 °C when the flow rates of the H₂–He feed and the nitrogen sweep were 40 mL min^?1 and 30 mL min^?1, respectively.     

Highly enhanced ammonia decomposition in a bimodal catalytic membrane reactor for COx-free hydrogen production

Ammonia decomposition in a bimodal catalytic membrane reactor (BCMR) consisting of a Ru/γ-Al₂O₃/α-Al₂O₃ bimodal catalytic support and a hydrogen-selective silica membrane in a single unit was proposed for CO_x-free hydrogen production in the present study. The bimodal catalytic membrane showed a H₂ permeance of 6.2 × 10^-7 mol/(m² s Pa) at 500 °C, with H₂/NH₃ and H₂/N₂ permeance ratios of 200 and 720, respectively. Ammonia conversion was surprisingly enhanced form 45 to 95% at 450 °C in the BCMR after selective H₂ extraction. The BCMR showed excellent stability with respect to both gas permeation properties and catalytic activities.     

Competition between 3d metals(II) and palladium(II) in the reaction of heterobimetallic complexes Pd(μ-OOCMe)4M(OH2) (M = Ni,Co, Mn) with azobenzene

The reaction of Pd^II(μ-OOCMe)₄M^II(OH₂) (M = Ni, Co, Mn) with azobenzene under mild conditions produces the homonuclear complex with ortho-metallated azobenzene (PhN = NC₆H₄)₂Pd₂(μ-OOCMe)₂ (4) in higher than 90 % yield as the sole Pd-containing reaction product, while the co-metals are recovered as the corresponding M^II acetates.     

Elucidation of hydrogen mobility in coal under reductive atmosphere using a tritium tracer method

Hydrogen exchange reaction of three Argonne coals (Illinois No. 6, Upper Freeport and Pocahontas #3) and Wandoan coal with tritiated gaseous hydrogen were performed at several temperatures. Hydrogen exchange reaction was performed in a flow reactor packed with 0.4 g of coal and 0.05 g of catalysts under the following conditions: pressure 15 kg/cm², temperature 200, 250, 300 °C, carrier gas H₂ or N₂ 5 ml/min. When a pulse of [³H]H₂ was introduced into a coal in H₂ carrier gas at several temperatures, the delay of [³H]H₂ pulse observed increased with increasing the reaction temperature and decreased with increasing coal rank. Further in the reaction of tritiated coals with gaseous hydrogen at constant temperature, the hydrogen exchange rate was estimated from the release rate of [³H]H₂. The apparent hydrogen exchange rate at 200 °C was higher than that at 250 °C. This shows that the hydrogen with low reactivity came to participate in the reaction at high temperature. When the reaction of tritiated coal with gaseous hydrogen was performed during heat treatment, one, two or three peaks of tritium concentration were observed in the outlet of the reactor depending on temperature (200, 250 or 300 °C, respectively) at which tritium was incorporated into coal initially. It was suggested that there were at least three kinds of hydrogen with different reactivity in coal.     

Was pretreatment beneficial for more biogas in any process? Chemical pretreatment effect on hydrogen–methane co-production in a two-stage process

The study focused on the mesophilic anaerobic hydrogen production from PPS (pulp and paper sludge) and FW (food waste) pretreated by NaOH or H₂SO₄, and the subsequent thermophilic anaerobic methane production with the effluent in a two-stage process. The maximum hydrogen yield (78.35 mL g^?1 VS_fed) which was 50.21% higher than that of CK, was achieved when 10 g NaOH/100 g TS_substrate was used. However, the maximum methane yield (383.8 mL g^?1 VS_fed) was obtained in CK as well as 64% SCOD removal efficiency was achieved. In short, NaOH/H₂SO₄ pretreatment was suitable to enhance the hydrogen production.     

Titania ultrafiltration membrane: Preparation,characterization and photocatalytic activity

A mesoporous photocatalytic titania (TiO₂) membrane on alumina support is successfully fabricated via the sol–gel processing method. Several techniques such as dynamic light scattering, X-ray diffraction (XRD), TGA, N₂-sorption, and SEM are utilized to investigate the optimized processing parameters and their influence on the final properties of the developed membrane. The prepared titania sol containing organic additives (HPC and PVA) has an average particle size of 55.6 nm with a narrow distribution. The resulting TiO₂ membrane with thickness of 1 μm exhibits homogeneity with no cracks or pinholes. It also maintains small pore size (4.7 nm), large specific surface area (75 m²/g), and small crystallite size (8.3 nm).The permeability and photocatalytic properties of the titania membrane were measured. The permeability coefficient of the fabricated membrane is 30.09 cm³ min^?1 bar^?1 cm^?2. These measurements indicate an optimum processing condition for the preparation of the membrane. The prepared titania membrane has a great potential in developing high efficient water treatment and reuse systems because of its multifunctional capability such as decomposition of organic pollutants and physical separation of contaminants.     

A novel BaCe0.5Fe0.3Bi0.2O3–δ perovskite-type cathode for proton-conducting solid oxide fuel cells

A perovskite-type BaCe_0.5Fe_0.3Bi_0.2O_3-δ (BCFB) was employed as a novel cathode material for proton-conducting solid oxide fuel cells (SOFCs). The single cells with the structure of NiO-BaZr_0.1Ce_0.7Y_0.2O_3-δ (BZCY7) anode substrate|NiO-BZCY7 anode functional layer|BZCY7 electrolyte membrane|BCFB cathode layer were fabricated by a dry-pressing method and investigated from 550 to 700 °C with humidified hydrogen (~3% H₂O) as the fuel and the static air as the oxidant. The low interfacial polarization resistance of 0.098 Ω cm² and the maximum power density of 736 mW cm⁻² are achieved at 700 °C. The excellent electrochemical performance indicates that BCFB may be a promising cathode material for proton-conducting SOFCs.     

Syntheses,structures, and properties of two dinuclear palladium (II) complexes of a single macrocyclic hexaaza ligand with two hydroxyethyl pendants

Two dinuclear palladium (II) complexes, trans-[Pd₂LCl₂](ClO₄)₂ · 2H₂O and cis-[Pd₂LCl₂]Cl₂ · 2H₂O, of a single macrocyclic ligand with two hydroxyethyl pendants, L (L = 3,6,9,16,19,22-hexaaza-6,19-bis(2-hydroxyethyl)tricyclo[22,2,2,2^11,14]triaconta-1,11,13,24,27,29-hexaene), have been synthesized as “inorganic proteases” and analyzed by X-ray diffraction method. The two complexes-mediated hydrolytic cleavage of amide bond in acetyl methionyl alanine has been monitored by ¹H NMR, showing a moderate hydrolytic rate at 50 °C and pH ca. 1.0. The pendent hydroxyl group is responsible for the hydrolytic reaction.     

Simple solid-state synthesis and improved performance of Ni(OH)2-TiO2 nanocomposites for photocatalytic H2 production

To reduce the cost of the traditional noble metal-loaded photocatalysts for H₂ production, low-cost Ni(OH)₂-TiO₂ nanocomposites were designed and synthesized by a simple room-temperature solid-state chemical method (RSCM), which is a facile, low-cost and eco-friendly manipulation. Various testing methods and tools were used to characterize the crystal structure, elemental composition, morphology, light absorption ability, fluorescent performance, photocurrent density, and photocatalytic activity of the obtained nanocomposites. The results indicated that RSCM can be used to synthesize Ni(OH)₂-TiO₂ nanocomposites with a small size (50 nm) and good dispersity. Compared to pure TiO₂, the obtained nanocomposites displayed excellent photocatalytic performance for H₂ production by photocatalytic water-splitting. The amount of hydrogen needed for the optional nanocomposite NOT-1 was 9180 μmol/g, which is 29 times that of the commercial P25. The reason for the improved performance for photocatalytic hydrogen production is that the existing Ni(OH)₂ in nanocomposites promoted the separation between the photogenerated electron and holes.     

Optimization of carbamazepine removal in O3/UV/H2O2 system using a response surface methodology with central composite design

This study used an ozone/ultraviolet/hydrogen peroxide (O₃/UV/H₂O₂) system to remove carbamazepine (CBZ) from water using a second-order response surface methodology (RSM) experiment with a five-level full-factorial central composite design (CCD) for optimization. The effects of both the primary and secondary interactions of the photocatalytic reaction variables, including O₃ concentration (X₁), H₂O₂ concentration (X₂), and UV intensity (X₃), were examined. The O₃ concentration significantly influenced CBZ and total organic carbon (TOC) removal as well as total inorganic nitrogen ion production (T-N) (p < 0.001). However, CBZ, TOC removal, and T-N production were enhanced with increasing O₃ and H₂O₂ concentrations up to certain levels, and further increases in O₃ and H₂O₂ resulted in adverse effects due to hydroxyl radical scavenging by higher oxidant and catalyst concentrations. UV intensity had the most significant effect on T-N production (p < 0.001). Complete removal of CBZ was achieved after 5 min. However, only 34.04% of the TOC and 36.99% of T-N were removed under optimal concentrations, indicating formation of intermediate products during CBZ degradation. The optimal ratio of O₃ (mg L^? 1): H₂O₂ (mg L^? 1): UV (mW cm^? 2) were 0.91:5.52:2.98 for CBZ removal, 0.7:18.93:12.67 for TOC removal, and 0.94: 4.85:9.03 for T-N production, respectively.     

Visible light assisted highly efficient hydrogen production from H2S decomposition by CuGaO2 and CuGa1−xInxO2 delafossite oxides bearing nanostructured co-catalysts

The present communication is the report of our research work on synthesis of new delafossite oxides containing Ga/Ga and In p-block elements, and their visible light driven catalytic activity in solar H₂ production from H₂S decomposition. CuGaO₂ and its indium doped analogue CuGa_1−xIn_xO₂ (x = 0.065) delafossite oxides without/with NiO and RuO₂ co-catalysts loading in nanostructures were prepared by solid state reaction method. These materials possess hexagonal rhombohedral structure (XRD); morphologically CuGaO₂ has irregularly-shaped plate like particles while all others have ordered hexagonal rod-like arrangements (FESEM). Co-catalyst deposits of few nm sizes are observable as white spots/patches on the surface of naked oxide catalysts. Acquiring p-type conductivity from the mixed valence of Cu (+1 and +2) and oxygen deficiency, these catalysts strongly absorb visible light (Eg = 1.85 eV) in a wide wavelength range. They decompose H₂S in aqueous 0.5 M KOH solution under visible light (λ ⩾ 420 nm) irradiation and generate H₂ to the tune of 4300 μmol/h, giving rise to a high quantum efficiency of 13.6% at 550 nm. The exceedingly higher rate of H₂ production appears to result from a combined contribution of chemical nature (p-block elements Ga and In), p-type conductivity and an efficient e⁻–h⁺ separation.