Improvement of high-rate capability of alkaline Zn–MnO2 battery

Electrolytic dendritic-zinc powders of high surface area are prepared from an alkaline solution by a galvanostatic electrodeposition method. The surface morphology and microstructure of these powders are examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Cylindrical AA-size alkaline zinc–manganese dioxide (Zn–MnO₂) batteries made with powders in anode gels are assembled and tested. The electrochemical characteristics of the batteries are evaluated by means of the ac impedance method and the constant-current discharge experiments. It is found that the high-rate performance of cells with dendritic-zinc powders is much better than that of cells with conventional molten-zinc powders.     

Recyclable CeO2–ZrO2 and CeO2–TiO2 mixed oxides based Pt catalyst for aqueous-phase reforming of the low-boiling fraction of bio-oil

In this study, a series of CeO₂–ZrO₂ and CeO₂–TiO₂ materials with different composition were prepared, characterized by BET and XRD analysis, and their hydrothermal stability was studied by subjecting the samples to acetic acid solutions at 533 K. All of the materials, especially C1Z1 (50 mol% CeO₂ with 50 mol% ZrO₂) and C1T1 (50 mol% CeO₂ with 50 mol% TiO₂), exhibited excellent stability with no phase transformation and minimal decrease in their specific surface area (SSA) was observed even after 16 h. After being loaded by Pt, these catalysts were used for the aqueous phase reforming (APR) of the low-boiling fraction of bio-oil (LBF) to investigate their catalytic performance. Among these catalysts Pt/C1Z1 and Pt/C1T1 showed superior catalytic activity, probably due to their lowest reduction temperature and the largest amount of O vacancies generated by the reduction of the surface oxygen of well-dispersed CeO₂. Thus, Pt/C1Z1 and Pt/C1T1 were chosen to investigate their recyclability. The catalytic activity and H₂ selectivity of Pt/C1Z1 and Pt/C1T1 can be almost recovered after being calcined in air at 773 K for regeneration. After three cycles, the particle size of Pt/C1Z1 and Pt/C1T1 only experienced a slight increase, while for Pt/Al₂O₃ it increased from 2.9 nm to 7.8 nm. So, compared with Pt/Al₂O₃, the Pt/C1Z1 and Pt/C1T1 catalysts were identified as effective and recyclable candidates for the production of H₂ rich fuel gas from APR of LBF.     

Characterization of RuO2·xH2O with various water contents

Hydrous ruthenium oxides (RuO₂·xH₂O) with different contents of water (x) were prepared by annealing commercial RuO₂·2.6H₂O powders at different temperatures. The morphologies and crystalline structures of RuO₂·xH₂O were investigated using transmission electron microscope (TEM) and selected area electron diffraction (SAED) techniques. From the TEM images, it was observed that the particle size of RuO₂·xH₂O increased with increasing annealing temperature. From the SAED patterns, it was observed that RuO₂·xH₂O powders became an amorphous phase at annealing temperatures <116 °C and became a crystalline phase at annealing temperatures above 116 °C. Amorphous RuO₂·xH₂O prepared at 116 °C reached its maximum specific capacitance as a result of proton insertion into the bulk of RuO₂ but with smaller Ru–Ru distance in the local structure. The more disordered structure induced by proton insertion was obtained by SAED pattern from a sample annealed at 116 °C. The possible connection between the microstructure and specific capacitance of RuO₂·xH₂O is discussed.     

Study of Ni/CeO2–ZnO catalysts in the production of H2 from acetone steam reforming

This paper reports the study of new Ni/ZnO-based catalysts for hydrogen production from substoichiometric acetone steam reforming (ASR). The effect of CeO₂ introduction is analyzed regarding the catalytic behavior and carbon deposits formation. ASR was studied at 600 °C using a steam/carbon ratio S/C = 1. Ni/xCeZnO (x = 10, 20, 30 CeO₂ wt %) catalysts showed a better performance than the bare Ni/ZnO. Ni/xCeZnO generated a lower amount and less ordered carbon deposits than Ni/ZnO. The higher the CeO₂ content in Ni/xCeZnO, the lower the amount of carbon deposits in the post-reaction catalyst. The highest H₂ production under ASR at the experimental conditions used was achieved for the Ni/xCeZnO catalysts. In-situ DRIFTS-MS experiments under ESR conditions showed different reaction pathways over Ni/20CeZnO and Ni/ZnO catalysts.     

What explain the short-term dynamics of the prices of CO2 emissions?

Using a Bayesian Structural VAR (BSVAR), this paper analyzes the short-term dynamics of the prices of CO₂ emissions in response to changes in the prices of oil, coal, natural gas and electricity. The results show that: (i) a positive shock to the crude oil prices has an initial positive effect on the CO₂ allowance prices, which later becomes negative; (ii) an unexpected increase in the natural gas prices reduces the price of CO₂ emissions; (iii) a positive shock to the prices of the fuel of choice, coal, has virtually no significant impact on the CO₂ prices; (iv) there is a clear positive effect of the coal prices on the CO₂ allowance prices when the electricity prices are excluded from the BSVAR system; and (v) a positive shock to the electricity prices has a negative impact on the price of the CO₂ allowances. We also find that the energy price shocks have a persistent impact on the CO₂ allowance prices, with the largest effect occurring 6 months after a shock strikes. The effect is particularly strong in the case of the shocks to the natural gas and crude oil prices. Finally, the empirical findings suggest an important degree of substitution between the three primary sources of energy (i.e., crude oil, natural gas and coal), particularly when electricity prices are excluded from the BSVAR system.     

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.     

Achievement of hydrogen production from autothermal steam reforming of methanol over Cu-loaded mesoporous CeO2 and Cu-loaded mesoporous CeO2–ZrO2 catalysts

Hydrogen production by oxidative steam reforming of methanol (OSRM) or autothermal steam reforming of methanol (ASRM) was investigated over Cu-loaded mesoporous CeO₂ and Cu-loaded mesoporous CeO₂–ZrO₂ catalysts, synthesized via a nanocasting process using MCM-48 as a hard template, followed by a deposition–precipitation technique. Various Cu contents were loaded on the mesoporous CeO₂ and CeO₂–ZrO₂ supports. The fresh and spent catalysts were characterized by N₂ adsorption–desorption, X-ray diffraction, temperature-programmed oxidation, and X-ray photoelectron spectroscopy. The ASRM results showed that 9 wt% Cu loading onto mesoporous CeO₂ and CeO₂–ZrO₂ provided the best catalytic performance with 100% methanol conversion and 60% H₂ yield at 350° and 300 °C, respectively. Furthermore, the time-on-stream stability testing of the 9 wt% Cu loading catalyst was at 168 h, and the CO selectivity of these two catalysts indicated that the addition of ZrO₂ into the catalyst reduced the CO selectivity during the ASRM process.     

Synthesis of heat exchanger networks featuring a minimum number of constrained-size shells of 1–2 type

In chemical plants requiring a high number of heat exchangers, standard sizes are established so that most of the services can be satisfied through arrays of a limited number of different standard-type units. If such an industrial practice is not taken into account during the heat recovery network synthesis task, the optimality of the proposed design could be doubtful. This paper addresses the HENS problem allocating multiple constrained-size shells rather than a single one to accomplish a heat match. Two cases are considered: (a) pure countercurrent exchangers and (b) shell-and-tube exchangers of 1–2 type. The neighbor-based HENS framework of Galli and Cerdá (1998) has been generalized in order to adopt a more realistic fixed-cost target, i.e. the overall number of constrained-size shells. Therefore, new 0–1 variables have been defined to stand for the additional shells needed to get both, a shell size below the specified upper bound, and simultaneously, an F_T correction factor above the threshold value everywhere. The resulting MILP problem formulation is now able to find network structures reaching the heat recovery target, under some structural constraints on the network design specified by the user, at near-minimum capital cost. The proposed algorithmic approach has been successfully applied to the solution of a couple of example problems and produced significant capital cost savings compared with prior HENS techniques.     

Effect of mineralizers for preparing ZrO2 support on the supported Ni catalyst for steam-CO2 bi-reforming of methane

Supported Ni catalysts on ZrO₂ towards steam-CO₂ bi-reforming (SCBR) of methane for the production of synthesis gas were synthesized by the hydrothermal process with different mineralizers followed by l-arginine ligand-assisted incipient wetness impregnation (HT-LA-IWI) method. The effect of type and amount of mineralizers for preparing ZrO₂ supports on the nature of supports and supported Ni catalysts, as well as on the catalytic properties and structure–performance relationship were investigated. Results show that the catalytic performance is strongly dependent on the morphology and textural of ZrO₂ support notably affected by the type and amount of mineralizer. The supported Ni catalyst on the ZrO₂ prepared by using sodium acetate (molar ratio of sodium acetate/zirconium, N_SAc/Zr = 0.5) as mineralizer (Ni/ZrO₂ (SAc0.5)) shows much higher catalytic activity than the one on ZrO₂ prepared by using sodium carbonate (molar ratio of sodium carbonate/zirconium, N_SC/Zr = 0.5) as a mineralizer (Ni/ZrO₂ (SC0.5)), ascribed to higher Ni dispersion and smaller average crystallite size of Ni. With respect to both activity and stability, the sodium acetate can be selected as a suitable mineralizer for the preparation of excellent ZrO₂ support. Furthermore, the increasing N_SAc/Zr from 0.5 to 2.0 leads to an increase in surface area but a decrease in pore diameter and pore volume, which endows the Ni/ZrO₂ (SAc2.0) catalyst with much larger average crystallite size of Ni but much worse Ni dispersion than Ni/ZrO₂ (SAc0.5). As a result, Ni/ZrO₂ (SAc2.0) shows much lower catalytic activity than Ni/ZrO₂ (SAc0.5). Moreover, the Ni/ZrO₂ (SAc2.0) catalyst shows worse Ni sintering resistance than Ni/ZrO₂ (SAc0.5) owing to its weaker NiZrO₂ interaction confirmed by H₂-TPR results, which endows it with lower catalytic stability although it has higher coke deposition resistance.     

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.     

Effects of CaO addition on Ni/CeO2–ZrO2–Al2O3 coated monolith catalysts for steam reforming of N-decane

A series of 10 wt%Ni/CeO₂–ZrO₂–Al₂O₃ (10%Ni/CZA) coated monolith catalysts modified by CaO with the addition amount of 1 wt%~7 wt% are prepared by incipient-wetness co-impregnation method. Effects of CaO promoter on the catalytic activity and anti-coking ability of 10%Ni/CZA for steam reforming of n-decane are investigated. The catalysts are characterized by N₂ adsorption-desorption, XRD, SEM-EDS, TEM, NH₃-TPD, XPS, H₂-TPR and Raman. The results show that specific surface area and pore volume of as-prepared catalysts decrease to some extent with the increasing addition of CaO. However, the proper amounts of CaO (≤3 wt%) significantly enhance the catalytic activity in terms of n-decane conversion and H₂ selectivity mainly due to the improved dispersion of NiO particles (precursor of Ni particles). As for anti-coking performance, reducibility of CeO₂ in composite oxide support CZA is promoted by CaO resulting in providing more lattice oxygen, which favors suppressing coke formation. Moreover, the addition of CaO reduces the acidity of 10%Ni/CZA, especially the medium and strong acidity. But far more importantly, a better dispersion of NiO particles obtained by proper amounts of CaO addition is dominant for the lower carbon formation, as well as the higher catalytic activity. For the spent catalysts, amorphous carbon is the main type of coke over 10%Ni–3%CaO/CZA, while abundant filamentous carbon is found over the others.     

Effect of RuO2–CoS2 anode nanostructured on performance of H2S electrolytic splitting system

An innovative, nanostructured composite, anode electrocatalyst, material has been developed for the electrolytic splitting of (100%) H₂S feed content gas operating at 135 kPa and 150 °C. A new class of anode electrocatalyst with general composition, RuO₂–CoS₂ has shown great stability and desired properties at typical operating conditions. This configuration showed stable electrochemical operation over the period of 24 h and also exhibited a maximum current density of (0.019 A/cm²). The kinetic behaviors of various anode-based electrocatalysts demonstrated that, exchange current density, which is a direct measure of the electrochemical reaction, increased with RuO₂–CoS₂-based anodes. Moreover, high levels of feed utilization were possible using these materials. Electrochemical performance, current density, and sulfur tolerance were enhanced compared to the other tested anode configurations. The structural, microstructural and surface behavior of RuO₂–CoS₂ anode electrocatalyst was investigated in detail.     

Kinetics and mechanism of CO2 gasification of coal catalyzed by Na2CO3, FeCO3 and Na2CO3–FeCO3

The purpose is to develop a mild catalytic CO₂-gasification technology that can promote CO₂ utilization and reduce cost in air separation systems with improving system efficiency and obtaining desirable gaseous products. In this study, the influence of Na, Fe and their composite catalysts on the structure and gasification reactivity of chars derived from pyrolysis of Powder River Basin (PRB) coal was investigated. The results showed that a strong positive synergistic effect between Na and Fe catalyst in the gasification process was observed, the catalytic activity of the added catalysts was in order of: 4% Na > 3% Na–1%Fe > 2% Na-2% Fe > 1% Na-3% Fe > 1% Na-2% Fe > 4% Fe > raw coal. The catalysts inhibited the growth of the aromatic ring structure and enriched the generation of O-containing functional groups. Compared to Fe, the Na-based catalyst could easily diffuse into inner pores of coal char, forming C–O–Na structure and thus increasing the gasification reactivity of chars. In addition, due to the formation of inert material between SiO₂ and Na, the catalytic activity of Na catalysts was significantly decrease at the late stage of char conversion. Comparatively, the Fe-based catalysts showed better stability life. Moreover, it was found that the activation energy for CO₂-gasification of PRB coal can be decreased by 50% due to the addition of Na catalyst.     

Fabrication and testing of a H2–O2 fuel cell using MoxRuySez

We report the results obtained in the preparation and characterization of Mo_xRu_ySe_z electrocatalysts for oxygen reduction reaction and the design, construction and characterization of a H₂–O₂ fuel cell using Mo_xRu_ySe_z. The catalysts were characterized with respect to their electrocatalytic properties. The fuel cell was designed and built with Mo_xRu_ySe_z supported on carbon as cathode, Pt supported on carbon as anode, and H₂SO₄ as the electrolyte. The fuel cell was tested at room temperature and atmospheric pressure. The H₂–O₂ cell showed an efficiency in the order of 30%.     

Synthesis of scalable 1T/2H–MoSe2 nanosheets with a new source of Se in basic media and study of their HER activity

In this report MoSe₂ nanosheets were fabricated using new precursors of MoCl₅ and Na₂SeO₃ and a very simple chemical procedure without using inert atmosphere and complex methods for preparing Se ion source. The structural properties of fabricated nanosheets were examined by means of XRD, field emission scanning electron microscopy (FESEM), elemental mapping of energy dispersive x-ray spectroscopy (EDS), transmission electron microscopy (TEM), atomic force microscopy (AFM), Raman spectroscopy and isotherm gas adsorption-desorption technique. The results showed the nanosheets are mixed phase metallic-semiconductor 1T-2H with thicknesses about 3.6–6.1 nm and are stable for several months. The effective surface area is obtained 28 m² g⁻¹ and mean pore size of 6–8 nm for MoSe₂ nanosheets. Electro-impedance spectroscopy showed low resistivity of nanosheets due to presence of metallic phase of MoSe₂. HER activity of nanosheets obtains a Tafel slope of 60 mV.dec⁻¹ and high current density values up to 150 mA cm⁻² and the value of over potential at 10 mA cm⁻² is 155 mV.     

Evaluating cubic equations of state for calculation of vapor–liquid equilibrium of CO2 and CO2-mixtures for CO2 capture and storage processes

Proper solution of vapor liquid equilibrium (VLE) is essential to the design and operation of CO₂ capture and storage system (CCS). According to the requirements of engineering applications, cubic equations of state (EOS) are preferable to predict VLE properties. This paper evaluates the reliabilities of five cubic EOSs, including PR, PT, RK, SRK and 3P1T for predicting VLE of CO₂ and binary CO₂-mixtures containing CH₄, H₂S, SO₂, Ar, N₂ or O₂, based on the comparisons with the collected experimental data. Results show that SRK is superior in the calculations about the saturated pressure of pure CO₂; while for the VLE properties of binary CO₂-mixtures, PR, PT and SRK are generally superior to RK and 3P1T. The impacts of binary interaction parameter k_ij were also analyzed. k_ij has very clear effects on the calculating accuracy of an EOS in the property calculations of CO₂-mixtures. In order to improve the calculation accuracy, the binary interaction parameter was calibrated for all of the studied EOSs regarding every binary CO₂-mixture.     

Effects of MoS2 addition on the hydrogen storage properties of 2LiBH4–MgH2 systems

A 2LiBH₄–MgH₂–MoS₂ composite was prepared by solid-state ball milling, and the effects of MoS₂ as an additive on the hydrogen storage properties of 2LiBH₄–MgH₂ system together with the corresponding mechanism were investigated. As shown in the TG–DSC and MS results, with the addition of 20 wt.% of MoS₂, the onset dehydrogenation temperature is reduced to 206 °C, which is 113 °C lower than that of the pristine 2LiBH₄–MgH₂ system. Meanwhile, the total dehydrogenation amount can be increased from 9.26 wt.% to 10.47 wt.%, and no gas impurities such as B₂H₆ and H₂S are released. Furthermore, MoS₂ improves the dehydrogenation kinetics, and lowers the activation energy (E_a) 34.49 kJ mol⁻¹ of the dehydrogenation reaction between Mg and LiBH₄ to a value lower than that of the pristine 2LiBH₄–MgH₂ sample. According to the XRD test, Li₂S and MoB₂ are formed by the reaction between LiBH₄ and MoS₂, which act as catalysts and are responsible for the improved hydrogen storage properties of the 2LiBH₄–MgH₂ system.     

Hydrogen production by steam reforming of liquefied natural gas (LNG) over Ni/Al2O3–ZrO2 xerogel catalysts: Effect of calcination temperature of Al2O3–ZrO2 xerogel supports

Al₂O₃–ZrO₂ (AZ) xerogel supports prepared by a sol-gel method were calcined at various temperatures. Ni/Al₂O₃–ZrO₂ (Ni/AZ) catalysts were then prepared by an impregnation method for use in hydrogen production by steam reforming of liquefied natural gas (LNG). The effect of calcination temperature of AZ supports on the catalytic performance of Ni/AZ catalysts in the steam reforming of LNG was investigated. Crystalline phase of AZ supports was transformed in the sequence of amorphous γ-Al₂O₃ and amorphous ZrO₂ → θ-Al₂O₃ and tetragonal ZrO₂ → (θ + α)-Al₂O₃ and (tetragonal + monoclinic) ZrO₂ → α-Al₂O₃ and (tetragonal + monoclinic) ZrO₂ with increasing calcination temperature from 700 to 1300 °C. Nickel oxide species were strongly bound to γ-Al₂O₃ and θ-Al₂O₃ in the Ni/AZ catalysts through the formation of solid solution. In the steam reforming of LNG, both LNG conversion and hydrogen composition in dry gas showed volcano-shaped curves with respect to calcination temperature of AZ supports. Nickel surface area of Ni/AZ catalysts was well correlated with catalytic performance of the catalysts. Among the catalysts tested, Ni/AZ1000 (nickel catalyst supported on AZ support that had been calcined at 1000 °C) with the highest nickel surface area showed the best catalytic performance. Well-developed and pure tetragonal phase of ZrO₂ in the AZ1000 support played an important role in the adsorption of steam and the subsequent spillover of steam from the support to the active nickel.