查看更多>>摘要：The structure, materials and transport kinetics of solid oxide cells (SOC's) and oxygen permeation membranes (OPMs) are quite similar, but a unified and explicit model is lacking. Here, a continuum model for evaluating the electrochemical performance and stability of SOC's and OPMs is developed based on linear irreversible thermodynamics. The oxygen partial pressure at the electrode/electrolyte interface is used to evaluate the stability of SOC's and OPMs, and is calculated by considering the gas exchange at the electrode/electrolyte interface and the mixed ionic and electronic conduction in the electrolyte. The calculation results are verified by the literature data. The effect of fundamental material properties on the SOC's and OPM's performance under certain operating conditions is studied via parametric scanning. In addition, the stabilities of the SOC's and OPMs are also discussed for various operating conditions. The results show that the open circuit voltage (OCV) and stability of SOC's under open-circuit is not only influenced by the magnitude of resistances of the electrolyte, and the air and fuel electrodes, but also the matching of them. Since the OPM can be regarded as the SOC under the open-circuit condition, the present model is also applicable for calculating the oxygen permeation flux. It is shown that the oxygen permeability is increased by lowering the OCV of the OPM. Optimization of SOFC's performance should consider the matching of the electrode and the electrolyte resistances and the effect of resistance on stability. The evaluation of the performance of SOECs should consider the achieved electrolytic current density combing with the Faradic efficiency. Promotion of the ionic and/or electronic conductivity of electrolytes can enhance the stability of SOECs, but should be treated carefully due to the sacrifice of Faradic efficiency.
查看更多>>摘要：Heteroatomic doped porous carbon (HPCs) is a promising advanced material, showing great application potential in greenhouse gas capture. Here, in-situ N-doped porous carbon (NPC) was developed via a novel and readily scalable strategy - one-step solvent-free melt polycondensation assisted by organic potassium salts, followed by pyrolysis and activation. As both a template and an activator, the added C6H5K3O7 played an important role to create abundant microporous structure. The as-fabricated NPC-650-0.5 showed a rich N content (6.11 at.%), abundant narrow micro-porosity (0.3437 cm~3·g~(-1)), and a high surface area (1209.37 m~2 - g~(-1)) and delivered an excellent CO2 static adsorption capacity (4.16 mmol · g~(-1) and 8.40 mmol · g~(-1) at 100 and 500 kPa), a fast adsorpti on kinetics (circa 98% of balance capacity in 12 min), moderate heat of adsorption (25 to 30 kJ/mol), high selectivity of CO2/N2, and outstanding uninterrupted recyclability. Both the narrow micropore volume and N-doping sites had strong effects on the CO2 adsorption capacity, indicating a physical and chemical adsorption process with the mechanism being multi-layer adsorption by the micropore filling. This work highlights the great potential of the NPC-650-0.5 for capturing CO2 and offers new insights into a green activator and a simple and easy-to-scale method for preparing HPCs.
查看更多>>摘要：Herein, a generalizable strategy using the solvothermal process to obtain the heterostructural composites between BiOBr nanosheet and CdS nanorods is presented. Using a facile hydrothermal method, the CdS nanorods were anchored onto BiOBr nanosheets with average scales ranging from 10 to 500 nm to build up the heterostructure. The improvement of the efficiency of charge separation through the construction of 2D/1D heterojunction was confirmed by SEM, TEM, XPS, photocurrent, and AC impedance. CO2 photoreduction was employed to study the photocatalytic activities of the as prepared composites. The heterostructural BiOBr/CdS composites owned better activity than both the pure BiOBr nanosheets and pure CdS nanorods. Most significantly, the yield of CO during photocatalytic reduction reaction with BiOBr/CdS-5% catalyst was measured to be 13.6 μmol g~(-1), which was 1.8 times larger than that with BiOBr nanosheets and 6.4 times larger than that with CdS nanorods during 3 h simulative sunlight exposure. The optimized photocatalytic property of heterostructural BiOBr/CdS-5% composite could be attributed to the wide sunlight response range, large specific surface area, and effective separation of photoelectrons-holes from the heterostructure between BiOBr nanosheets and CdS nanorods.
查看更多>>摘要：Integrated CO2 capture and utilisation (ICCU) is a promising strategy for restricting carbon emissions and achieving carbon neutrality. Bifunctional combined materials (BCMs), containing adsorbents and active catalysts, are widely applied in this process. Producing syngas via reverse water-gas shift reaction (RWGS) and integrating with Fischer-Tropsch (F-T) synthesis is an attractive and valuable CO2 utilisation route. This work investigated a series of Ni/support-CaO BCMs (supports = ZrO2, TiO2, CeO2 and Al2O3) for the integrated CO2 capture and RWGS (ICCU-RWGS) process. The Ni/support-CaO BCMs were prepared by physically mixing various metal oxide supports loaded Ni with sol-gel derived CaO. The ICCU-RWGS performance (CO2 conversion, CO yield and CO generation rate) of these BCMs followed the order during tested conditions (550-750 °C): Ni/CeO2-CaO>Ni/TiO2-CaO>Ni/ZrO2-CaO>Ni/Al2O3-CaO. A comprehensive characterisation of Ni/support materials showed that Ni/CeO2 had the characteristics of stronger basicity, optimal Ni dispersion and improved NiO reducibility, which led to the outperforming ICCU-RWGS activity over Ni/CeO2-CaO (e.g. 56.1% CO2 conversion, 2.68mmol g~(-1) CO yield and -100% CO selectivity at 650 °C). Furthermore, the Ni/CeO2-CaO BCM showed a stable, yet, self-optimising catalytic performance during the cyclic ICCU-RWGS reaction over 20 cycles. The TEM characterisation suggested that was ascribed to the volume expansion and shrinkage of CaO in the cyclic adsorption-desorption altering the distance between the adsorbent and Ni/CeO2, resulting in an enhanced CO2 conversion during the cycle.
查看更多>>摘要：Membrane separation technology offers the unique advantages in oily wastewater treatment. However, the oily wastewater in petrochemical industry often contains oil emulsions and soluble organic pollutants, which pose great obstacles to membrane materials. Herein, to address the aforementioned challenges, a multifunctional fibrous composite membrane (FCM) was prepared by simple spraying of three-dimensional (3D) TiO2@crumpled graphene oxide (GO) core-shell sphere onto electrospun poly (arylene ether nitrile) (PEN) porous support. In the hierarchical skin layer of composite membrane, the TiO2 nanoparticles were anchored onto 3D crumpled graphene oxide sphere surface assisted by the mussel-inspired dopamine coating, which further triggered the formation of chemical cross-linking networks and hydrogen bond interaction with tannic acid. Such rational design not only ensured the structure stability of the functional layer, but also achieved the extraordinary versatility and high separation efficiency compared the conventional two-dimensional GO stacked lamellar membranes. Due to the super-hydrophilicity/underwater hydrophobic feature, low oil adhesion, and well-regulated water channels, the GO@TiO2/PEN FCM exhibited superior permeance for various surfactant free (4830-5160 L·m~(-2)·h~(-1)) and stabilized oil-in-water emulsions (3142-3514 L·m~(-2)·h~(-1)) while keeping stable rejection rate over 99%. Moreover, the combination of TiO2 nanoparticles and GO endowed the FCM with synergistically enhanced photo catalytic degradation performance for the soluble organics. Under visible light irradiation, the degradation rate of methylene blue (MeB) and crystal violet (CV) could reach 90.8% and 92.5% in 60 min, respectively. Therefore, combination of high permeability and efficient photocatalytic degradation of the soluble organics enable the fibrous composite membrane to realize the fast separation of multi-component pollutant-oil-water emulsion.
查看更多>>摘要：Herein, lanthanides (Samarium: Sm, Lanthanum: La, and Erbium: Er) adsorption mechanism over copper trimesate metal-organic framework (Cu-BTC MOF) was studied. The MOF crystallized as [Cu(HBTC)(H2O}3] and [Cu3(BTC)2] with a rod-like structure and abundant free -COOH groups. The Langmuir adsorption capacity of 1007.1, 656.5, and 410.5 mg g~(-1) was recorded for Sm, La, and Er, respectively. The adsorption process was driven by rapid ion exchange with crystal structure transformation in the first hour of mixing, mediated by the surface ion-exchange phenomenon and free -COOH groups. After 1 h, the process was driven by a slow ion-exchange mechanism where Ln ions drifted internally, and Cu ions moved out towards the surface. Among the three lanthanides studied, Er/Cu-BTC system was more sensitive to structural reorganization with the increasing Ln/Cu ratio. The work reported here is one of the first detailed accounts of the Ln-adsorption process in MOFs.
查看更多>>摘要：In recent years, a new strategy of using sulfite (S(IV)) to replace persulfates (peroxydisulfate (PS) and peroxybisulfate (PMS)) for sulfate radical based advanced oxidation process (SR-AOP) has emerged as one of the potential alternatives in the field of AOPs. Although the thermal activation of PS and PMS has been investigated extensively, that of S(IV) has not yet been explored. In this work, As(III) oxidation in a heat-S(IV) system was investigated first to demonstrate the feasibility of thermal activation of S(IV). Results showed that S(IV) can be activated to oxidize As(III) by heating the reactant solution from room temperature to above 50°C. Almost complete oxidation of 5 μM As(III) in water at pH 7 with addition of 1 mM S(IV) was achieved at 70 °C within 30 min. As(III) oxidation in the heat-S(IV) system was strongly dependent on the dissolved oxygen in water. Radical-scavenging experiments and electron spin resonance analysis demonstrated that the main active species responsible for As(III) oxidation was SO4~(·-). On the basis of thermal activation, a new system of SR-AOPs, namely, heat-electro-S(IV) system, the coupling thermal and electrochemical activations was established with ruthenium-plated iridium electrodes at a voltage of 3 V. It achieved complete oxidation of 50 μM As(III) in water at pH 7 at 50 °C with the addition of 2 mM S(IV) after reaction for 30 min. This work provides a new activation method for SR-AOPs with S(IV) as the precursor of reactive species and helps in understanding the reaction of S(IV) auto oxidation.
查看更多>>摘要：Herein, dielectric barrier discharge (DBD) plasma and MnO2-cellulose acetate (MnO2/CA) composite films was coupled together to degrade sulfamethoxazole (SMX) in water. The MnO2/CA composite films were firstly prepared successfully though heating blending method in this study and then characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Raman spectra, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TG). Catalytic effect of the MnO2/CA films was investigated by comparing the removal percentages, the kinetic constants, the energy utilization efficiencies (G_(50)) as well as the COD and TOC removal during the SMX degradation in the DBD plasma system with or without the MnO2/CA films addition under different reaction conditions. The optimal catalytic performance was obtained by adding the 3% MnO2/CA films into the DBD plasma system and the alkaline solution condition was favorable for the SMX degradation. After four times using, the MnO2/CA composite films still maintained the catalytic activity. Catalytic mechanism of the MnO2/CA films was speculated by analyzing the changes of solution pH and conductivity during the reaction, concentrations of the formed O3 and H2O2 in water and the generated active species (~1O2 and · OH) in both the DBD plasma system and the DBD-MnO2/CA films system. The quenching test was also carried out to figure out the important effect of the ·O2~-, ~1O2 and · OH for the SMX degradation in the synergistic system. Finally, LC-MS was used to analyze the main intermediates generated during the SMX degradation and the possible degradation pathways were accordingly speculated. The research could provide a new direction for the development and application of the DBD plasma technology as well we the composite films catalyst.
查看更多>>摘要：Dielectric barrier discharge (DBD) plasma system coupled with titanium dioxide/reduced graphene oxide (TiO2/rGO) nanocomposites for enhanced hexavalent chromium (Cr(VI)) reduction has explored. TiO2/rGO nanocomposites were prepared by a modified hydrothermal method. The characterization of morphology, structure and optical properties showed that the TiO2/rGO nanocomposites could be successfully synthesized with large specific surface area and high charge carrier separation rate. The effects of the discharge voltage, initial concentration and solution pH on the reduction of Cr(VI) in the alone DBD system were experimentally analyzed. The results exhibited that the reduction efficiency of 100 mg/L Cr(VI) was 100% after 55 min discharge treatment at the discharge voltage 22 kV and at pH = 2. Moreover, the results of the DBD-TiO2/rGO system showed that the Cr(VI) reduction efficiency was greatly improved from 72% to 100% after 40 min discharge treatment with adding 0.3 g/L TiO2/rGO-S nanocomposite, indicating the TiO2/rGO nanocomposites exhibited greatly synergistic effect with DBD plasma. To illustrate the mechanism of Cr(VI) reduction in DBD combined with TiO2/rGO nanocomposites, quenching tests were performed by adding active species scavengers and the concentrations of H2O2 and O3 were also detected. Photogenerated electrons, ·O2~- and photo-generated H2O2 were found to play a vital role in accelerating the reduction of Cr(VI) to Cr(III).
查看更多>>摘要：Taking chlorobenzene (C6H5Cl) and o-dichlorobenzene (C6H4Cl2) as representatives of chlorobenzene based volatile organic compounds (CBs), a novel deep-purification technology of absorbing with ionic liquids (ILs) as absorbent was proposed and systematically investigated. Based on conductor-like screening model for real solvents (COSMO-RS) model, the suitable IL l-ethyl-3-methylimidazolium tetrafluorob orate ([EMIM][BF4]) for absorbing CBs was screened out from 289 kinds of commonly used ILs. Removal experiments of C6H5Cl and C6H4Cl2 by [EMIM] [BF4] were carried out at different temperatures, pressures and IL flow rates. Results suggested that [EMIM][BF4] had excellent absorption properties, and deep removal of CBs can be achieved that the content of C6H5Cl/C6H4Cl2 in the purified gas can be decreased down to 13.6 ppm/9.9 ppm (in molar fraction). Absorption capacity of [EMIM][BF4] to CBs was almost unchanged after absorbing and desorbing for up to 20 times, proving the repeatability of the absorption performance. Characterization by NMR and FT-IR showed that there was no chemical bond formed between [EMIM][BF4] and CBs, proving that the absorption process was physical absorption. Moreover, the structure of the regenerated [EMIM][BF4] had not been changed, which indicates that [EMIM][BF4] has strong thermal stability and chemical stability. Finally, the interaction mechanisms between [EMIM][BF4] and CBs were clarified from the aspects of interaction energy and interaction sites by quantum chemical calculation and wave function analysis. This work fills the gap of removing CBs by absorption method with ILs, and proved that ILs could be employed as promising green solvents for chlorobenzene based VOCs removal.
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