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To address the intrinsic limitations of both TiO2 and MXenes, we propose an effective strategy for the engineering of a 3D Ti3C2/TiO2 nanorod hybrid, where the in situ synthesized TiO2 nanorods are homogeneously decorated onto the surface of 3D Ti3C2 MXene via simple oxidation. As the LIB anode, it demonstrates exceptional long-term cycling stability with a specific capacity of 384.1 mA h g−1 after 600 cycles at 1.0 A g−1. [ABSTRACT FROM AUTHOR]

A vertically-stacked MXene/rGO composite membrane with ultrashort transport channels is reported here, which demonstrated outstanding molecular sieving, i.e., H2/CO2 selectivity of up to 83 together with high H2 permeance of 2.7 × 10−7 mol m−2 s−1 Pa−1 at 120 °C, highlighting its applicability for H2/CO2 separation in CO2 capture and sequestration. [ABSTRACT FROM AUTHOR]

Biomass-derived carbon materials have received a surge of scientific attention to develop lightweight and broadband microwave absorbers. Herein, rodlike porous carbon materials derived from cotton have been fabricated with uniformly dispersed CoFe2O4 nanoparticles via facile and scalable process. The combination of magnetic particles and carbonaceous material is advantageous to realize the magnetic-dielectric synergistic effect which could effectively promote the dissipation of incident waves, giving rise to an optimal reflection loss value of â€"48.2 dB over a qualified bandwidth (4.8 GHz) at 2.5 mm. The cotton-derived carbon rods with conductive network not only act as a supporter to carry the CoFe2O4 nanoparticles, but also provide massive heterointerfaces to facilitate the interfacial polarization. In consideration of the renewable and abundant resource of cotton, the as-prepared CoFe2O4/C composites would meet the increasing demand of lightweight and highly efficient microwave absorbers. [ABSTRACT FROM AUTHOR]

Mixed ionic‐electronic conducting La0.8Ca0.2Fe0.95O3−δ‐Ag (LCF‐Ag) ceramic hollow fiber membranes possess high structural stability and up to 2.24‐fold higher oxygen permeation fluxes relative to LCF hollow fibers. In this work, the oxygen permeation of LCF‐Ag hollow fiber membrane module is simulated under sweep gas and vacuum operation modes, whereas the kinetic parameters were obtained by fitting the experimental data with the simplified Tan–Li model. The good correlation obtained from the data regression confirmed the compatibility of the selected model on the LCF‐Ag hollow fiber membrane. The simulated results revealed that the countercurrent flow configuration is generally favored in sweep gas operation given its potential of complete oxygen separation under optimized conditions. For vacuum operation, the oxygen yield is practically the same for both flow configurations at a moderate vacuum setting. At a very low vacuum pressure setting, however, cocurrent flow is preferred over countercurrent flow for maximizing the oxygen yield. [ABSTRACT FROM AUTHOR]

Hydrogen fuel has been embraced as a potential long-term solution to the growing demand for clean energy. A membrane-assisted separation is promising in producing high-purity H2. Molecular sieving membranes (MSMs) are endowed with high gas selectivity and permeability because their well-defined micropores can facilitate molecular exclusion, diffusion, and adsorption. In this work, MXene nanosheets intercalated with Ni2+ were assembled to form an MSM supported on Al2O3 hollow fiber via a vacuum-assisted filtration and drying process. The prepared membranes showed excellent H2/CO2 mixture separation performance at room temperature. Separation factor reached 615 with a hydrogen permeance of 8.35 × 10−8 mol·m−2·s−1·Pa−1. Compared with the original Ti3C2Tx/Al2O3 hollow fiber membranes, the permeation of hydrogen through the Ni2+-Ti3C2Tx/Al2O3 membrane was considerably increased, stemming from the strong interaction between the negatively charged MXene nanosheets and Ni2+. The interlayer spacing of MSMs was tuned by Ni2+. During 200-hour testing, the resultant membrane maintained an excellent gas separation without any substantial performance decline. Our results indicate that the Ni2+ tailored Ti3C2Tx/Al2O3 hollow fiber membranes can inspire promising industrial applications. [ABSTRACT FROM AUTHOR]

Hydrogen (H2) is a clean energy carrier and its cost-effective separation is important for future H2 energy deployment. Currently, H2 is mainly produced from high temperature methane steam reforming reactions and thus the availability of membrane separation technology that can work at elevated temperatures can reduce the production cost. In this work, a cross-linked polybenzimidazole (PBI)-triglycidylisocyanurate (TGIC) and sulfonated graphene (SG) composite membrane was developed using a mixed proton–electron conducting concept. In such a membrane, protons diffuse by hopping along the cross-linking sites between the sulfonic groups of SG and the pyrrole rings of PBI, while electrons are transported via highly electron conductive SG. Following the addition of SG, the membrane became more compact, given the reduced interlayer spacing and swelling ratio. The thermal stability and oxidative resistance are comparable to those of other PBI-based membranes. For H2/CO2 separation, H2 can permeate through a 132 μm-thick membrane with 99.99% selectivity and a high flux of up to 0.22 mL min−1 cm−2 at 300 °C. The stable operation at 280 °C for 160 hours proves the membrane robustness at such an elevated temperature. Compared to the previously reported mixed conducting ceramic membranes exhibiting equivalent H2 fluxes requiring operation temperatures above 800 °C, the polymer and graphene composite membrane presented herein can reduce the operation temperature by 500 °C. This is an important requirement to ensure a more practical integration of membrane technology into industrial processes. [ABSTRACT FROM AUTHOR]

New CO2‐resistant dual‐phase Sm0.2Ce0.8O1.925–SrCo0.4Fe0.55Zr0.05O3‐δ (SDC‐SCFZ) ceramics present a promising outlook for potential future applications in membrane reactors and solid oxide fuel cells. Their high oxygen permeation flux and stability in CO2 sweep gas also allow their integration in oxyfuel combustion. Here the structural characteristics, electrical conductivities, thermal expansion behaviors, and oxygen permeabilities of four different SDC‐SCFZ membranes with weight ratios of 10:90, 25:75, 50:50, and 75:25 (SDC:SCFZ) are systematically studied. Among these four SDC‐SCFZ compositions, 0.6 mm‐thick 25 wt% SDC‐75 wt% SCFZ displayed the highest oxygen permeation fluxes that reach 1.26 mL min−1 cm−2 at 950°C and retained its phase integrity under alternating He and CO2 sweep gas over 72 hours of operation. This composite also showed a moderate thermal expansion coefficient of 1.90 × 10−5 K−1 between 30°C and 1000°C and an electrical conductivity of at least 16 S cm−1 at 550°C and above. Modeling studies revealed that the oxygen permeation fluxes through 25SDC‐75SCFZ are limited by surface exchange reactions from 700°C to 800°C and mixed bulk diffusion and surface exchange reactions above 800°C. [ABSTRACT FROM AUTHOR]

Ce0.85Sm0.15O1.925–Sm0.6Sr0.4Al0.3Fe0.7O3‐δ (SDC‐SSAF) hollow fiber membranes aimed for oxyfuel application are fabricated via a phase inversion‐sintering technique using powders synthesized from EDTA–citrate complex method. Oxygen ions transport is revealed to be the limiting step that determines the overall oxygen transport rate in SDC‐SSAF. SDC‐SSAF hollow fiber membrane attained a maximum flux of 2.6 ml min−1 cm−2 at 950°C under an oxygen partial pressure difference of 1/0.02 atm (feed/permeate). Variation in oxygen partial pressure on the permeate side exerts larger influence on the oxygen permeation flux relative to the change on the feed side. Stability tests over 100 h demonstrate stable oxygen permeation flux under both He and CO2 sweep conditions. [ABSTRACT FROM AUTHOR]

Direct carbon solid oxide fuel cell (DC‐SOFC) is a promising energy conversion system, which can directly convert the chemical energy of biomass into electrical energy with high efficiency and low pollution. Herein, a microtubular DC‐SOFC fueled with the biochar derived from pepper straw for electrical power generation is reported. The DC‐SOFC operated on pepper straw char gives a maximum power density of 217 mW cm−2, comparable with 252 mW cm−2 for that with hydrogen fuel at 850 °C. Moreover, the lifetime of the DC‐SOFC reaches 21 h at a discharge current of 100 mA with the fuel utilization of 44.4%. The pepper straw char is characterized physically by scanning electron microscopy, energy‐dispersive spectrometer, X‐ray diffraction, Raman spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. The results demonstrate that the pepper straw char contains natural catalysts in itself and their contribution on the electrochemical performance of the microtubular DC‐SOFC is analyzed in detail. [ABSTRACT FROM AUTHOR]

Reverse water‐gas shift reaction (RWGS) is important in the CO2 utilization cycle to convert carbon dioxide (CO2) and hydrogen (H2) to carbon monoxide (CO). In this work, the RWGS performance is evaluated by utilizing Ti4O7‐doped SrCe0.9Y0.1O3‐δ (SCY‐b) hollow fibre membrane reactor where H2 permeates through the SCY‐b proton conducting membrane and reacts with CO2 feed gas. Upon increasing the temperature from 750 to 950 °C, the CO yield increased from a negligible value to 14.82 %, when the sweep gas flow rate was 50 mL min−1 H2‐He (50:50 vol. ratio) and the feed gas flow rate was 100 mL min−1 CO2‐N2 (5:95 vol. ratio). The CO yield increase with the temperature increase reflects the enhanced H2 permeation flux through the SCY‐b membrane at higher temperatures. Higher CO2 concentration in the feed gas led to lower CO yield due to the higher amount of remaining CO2 in the outlet stream. The deposition of porous SCY or SCY‐b surface layer onto the hollow fibre outer circumference surface also increased H2 flux through the fibre relative to the non‐deposited one. Thermogravimetric and CO2‐temperature programmed desorption results further reveal that SCY‐b adsorbed CO2 at temperature above 500 °C due to the reaction between CO2 and SCY‐b material. Despite the formation of SrCO3 during RWGS, the SCY‐b hollow fibre membrane reactor still displayed a stable CO yield of around 14 % throughout the 6‐day continuous membrane reactor test. [ABSTRACT FROM AUTHOR]

In this work, hydrogen (H2) permeation fluxes through 230 nm‐thick graphene oxide (GO) membrane deposited on porous YSZ hollow fiber were measured and correlated to an explicit H2 permeation model. H2 fluxes through such GO‐YSZ hollow fiber membrane increased from 4.83 × 10−8 mol cm−2 s−1 to 2.11 × 10−7 mol cm−2 s−1 with temperature rise from 20 to 100 °C. The activation energy of H2 permeation was determined by the linear regression of the experimental data and was applied in the theoretical calculations. The model predictions fit well the temperature dependent and the argon sweep gas flow rate dependent H2 fluxes data. Using the derived permeation model, the effects of vacuum pressure at lumen side and H2 partial pressure at shell side, membrane area, and GO membrane film thickness on the membrane performance were simulated and discussed to provide insights for practical applications. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2711–2720, 2018 [ABSTRACT FROM AUTHOR]

Here, oxygen fluxes through an electronically short-circuited asymmetric Ag-YSZ|YSZ|LSM-YSZ hollow fiber prepared via a combined spinning and sintering route were tested and correlated to an explicit oxygen permeation model. The average oxygen permeation through such asymmetric hollow fiber with a 27 μm-thick YSZ dense layer reached 0.52 mL (STP) cm−2 min−1 at 1173 K. From the model results, we can obtain the characteristic thickness, the effects of the temperature, and the effect of He sweep gas flow rate to the individual step contribution. The oxygen partial pressure variation in the permeate side, the local oxygen flux, and the three-different resistance distribution along the axial direction of the asymmetric hollow fiber are theoretically studied; providing guidelines to further improve the membrane performance for oxygen separation. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3491-3500, 2017 [ABSTRACT FROM AUTHOR]

Electronically short-circuited ion conducting fluorite membranes for air separation are a relatively novel category of ceramic membranes overcoming the long-standing stability problem of the state-of-the-art perovskite membranes under reducing and acidic conditions. Such robust membranes have particular potential to further improve the economics of clean energy projects and syngas production. In this work, we adopted the conventional dual-phase membrane idea to decorate the fluorite membrane surface. Previously, a pure noble metal layer was employed as an electronic decoration layer which displayed several limitations. In this work, instead, a dual-phase mixture of Ce0.9Gd0.1O2−δ (50 wt%)–Ag (50 wt%) was applied as the decoration layer of the Ce0.9Gd0.1O2−δ bulk membrane. Such a strategy not only reduces the material cost and enhances the interface adherence but also significantly improves the O2 flux rates as more triple-phase boundary area is created for surface O2 exchange reactions. We further confirm the stability of the resultant short-circuited Ce0.9Gd0.1O2−δ membrane during the 130 hour permeation test at high temperatures under a CO2 containing atmosphere. [ABSTRACT FROM AUTHOR]

Micro-tubular SOFCs have the potential to become light-weight portable auxiliary power units for aircraft or spacecraft. In this work, a novel dual-layer ceramic hollow fiber for a cathode-supported micro-tubular solid oxide fuel cell (MT-SOFC) has been successfully developed via a co-spinning-sintering technique. The green cathode hollow fibers, in dual layer configuration, consisting of a La0.8Sr0.2MnO3-δ (LSM) main layer and a LSM-Y2O3 stabilized ZrO2 (YSZ) functional layer with increased three phase boundary length, are first prepared by co-spinning, which are then sintered at around 1350 °C to allow the creation of sufficient mechanical strength. Other cell components like the electrolyte (YSZ) and anode (NiO + YSZ) are then coated separately. The coated electrolyte film with a thickness of around 27 μm is obtained by co-sintering of YSZ/LSM-YSZ/LSM in a sandwich structure. The porous LSM substrate functions as an oxygen-supplying and current collecting layer. The prepared MT-SOFC, tested with hydrogen as the fuel and air as the oxidant, delivers a maximum power density of up to 475 mW cm-2 at 850 °C, which is much higher than that of a similar cell without a cathode functional layer. [ABSTRACT FROM AUTHOR]

Yttria-stabilized zirconia (YSZ) micro tubular electrolyte membranes for solid oxide fuel cells (SOFCs) were prepared via the combined wet phase inversion and sintering technique. The as-derived YSZ micro tubes consist of a thin dense skin layer and a thick porous layer that can serve as the electrode of fuel cells. The dense and the porous electrolyte layers have the thickness of 3–5 μm and 70–90 μm, respectively, while the inner surface porosity of the porous layer is higher than 28.1%. The two layers are perfectly integrated together to preclude the crack or flake of electrolyte film from the electrode. The presented method possesses distinct advantages such as technological simplicity, low cost and high reliability, and thus provides a new route for the preparation of micro tubular SOFCs. [ABSTRACT FROM AUTHOR]

Clarifying the mechanism for the gas transportation in the emerging 2D materials-based membranes plays an important role on the design and performance optimization. In this work, the corresponding studies were conducted experimentally and theoretically. To this end, we measured the gas permeances of hydrogen and nitrogen from their mixture through the supported MXene lamellar membrane. Knudsen diffusion and molecular sieving through straight and tortuous nanochannels were proposed to elucidate the gas transport mechanism. The average pore diameter of 5.05 Å in straight nanochannels was calculated by linear regression in the Knudsen diffusion model. The activation energy for H2 transport in molecular sieving model was calculated to be 20.54 kJ mol−1. From the model, we can predict that the gas permeance of hydrogen (with smaller kinetic diameter) is contributed from both Knudsen diffusion and molecular sieving mechanism, but the permeance of larger molecular gases like nitrogen is sourced from Knudsen diffusion. The effects of the critical conditions such as temperature, the diffusion pore diameter of structural defects, and the thickness of the prepared MXene lamellar membrane on hydrogen and nitrogen permeance were also investigated to understand the hydrogen permeation difference from Knudsen diffusion and molecular sieving. At room temperature, the total hydrogen permeance was contributed 18% by Knudsen diffusion and 82% by molecular sieving. The modeling results indicate that molecular sieving plays a dominant role in controlling gas selectivity. [ABSTRACT FROM AUTHOR]

The performance of direct carbon solid oxide fuel cells (DC‐SOFCs) is limited by the slow carbon gasification kinetics at operating temperatures. To address this limitation, a carbon fuel loaded with Ba catalyst is developed for DC‐SOFCs to improve the electrochemical performance in this study. Ba is loaded on activated carbon in the form of BaCO3 by the wet agglomeration technique. The effect of the Ba catalyst with various contents on the electrochemical performance in single cells and fuel utilization of DC‐SOFCs are examined. Experimental results show that the optimized Ba content is 5 wt% and the DC‐SOFC with this Ba‐loaded activated carbon fuel gives the best output with a maximum power density of 328.4 mW cm−2 at 850 °C. Furthermore, the DC‐SOFC fueled by 5 wt% Ba‐loaded activated carbon operates steadily for 28.76 h with the fuel utilization of 16.0%, which is also superior to many other cells. The enhancement of cell performance suggests that Ba is an effective catalyst to the Boudouard reaction, and the catalytic mechanism is also discussed in detail. [ABSTRACT FROM AUTHOR]

A correction to the article "Oxygen permeation behavior through Ce0.9Gd0.1O2-δ membranes electronically short-circuited by dual-phase Ce0.9Gd0.1O2-δ-Ag decoration" that was published in the 2015 issue is presented.