In recent years, the utilization of ionic liquids supported on porous polymer membranes has been demonstrated to enhance gas separation performance by improving both permeability and selectivity for ...several industrially-relevant gas mixtures. However, the use of such supported ionic liquid membranes (SILMs) is normally not feasible at elevated process temperatures due to the resulting decrease in ionic liquid viscosity, which can lead to increased loss of ionic liquid from the membrane support during operation. In addition, many of the polymer membranes typically used in SILMs exhibit relatively poor mechanical and thermal stabilities at high temperatures. To overcome these problems associated with SILMs, thermally-stable composite ionic liquid and polymer membranes (CILPMs) have been fabricated in this study, thus exploiting the beneficial properties of ionic liquids for gas separation at elevated temperatures. Poly(pyromellitimide-co-4,4′-oxydianiline) (PMDA-ODA PI) and polybenzimidazole (PBI) in combination with the ionic liquid, C4mimNTf2 were used to fabricate the CILPMs. A measurement rig was designed and built to determine permeabilities and selectivities of the CILPMs for H2, N2, CO, CO2 and CH4 over a range of pressures and temperatures. The fabricated CILPMs were shown to maintain excellent mechanical and thermal stability over a wide range of processing conditions. Temperature was shown to greatly affect both permeability and selectivity of the membranes, whilst pressure had less influence. The incorporation of C4mimNTf2 into the membranes was found to significantly increase CO2 permeation and, therefore, it is anticipated that these CILPMs hold significant potential for CO2 separation applications.
•Thermally-stable composite ionic liquid/polymer membranes (CILPMs) were fabricated.•Excellent mechanical and thermal stability over a wide range of conditions.•Measurement rig designed and built to determine gas permeabilities/selectivities.•C4mimNTf2 in membranes found to significantly increase CO2 permeation.•These CILPMs hold significant potential for CO2 separation applications.
Boron and nitrogen-dual-doped graphene sheets was facilely synthesized and it highly improved Pt for ORR.
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•A novel strategy for the facile synthesis of boron and nitrogen-dual-doped ...graphene sheets (BNG) is reported.•The synergistic improvement of BNG on Pt for ORR is investigated for the first time.•The BNG ingeniously anchor Pt nanoparticles ensuring Pt/BNG an excellent durability.•The Pt/BNG catalyst shows 60mV more positive half-wave potential and nearly three times the mass activity compared with Pt/C.
Boron and nitrogen-dual-doped graphene sheets (BNG) has been conveniently synthesized by a novel strategy, including one-step pyrolysis of nitrogen and boron-containing borane-tert-butylamine complex impregnated with cobalt ions. The BNG with a relatively high boron and nitrogen-doping level is used it as Pt support for oxygen reduction reaction for the first time. An excellent electron-donating of BNG to Pt that facilitates the reduction of O2 and strengthens BNG/Pt interaction has been evidenced. The novel Pt/BNG catalyst exhibits highly improved electrocatalytic activity and stability compared with commercial Pt/C. In O2-saturated 0.1M HClO4, the Pt/BNG catalyst shows a mass activity of 213.6mAmg−1Pt at 0.9V vs. RHE, which is nearly three times as high as that of commercial Pt/C. In addition, the Pt/BNG catalyst displays much higher stability than Pt/C in continuous potential cycling tests.
Elucidating the specific interaction between graphene with various structures and asphalt is essential to promote the wide adoption of graphene modified asphalt for high-performance pavement ...engineering. Herein, the enhancement of modified asphalts with nano-sized graphene (NG) and micro-sized graphene (MG) were systematically investigated by using dynamic shear rheometer (DSR), atomic force microscopy (AFM) and molecular dynamics (MD) simulation at multi-scale levels. The results demonstrate that MG can significantly enhance the deformation resistance and low-temperature crack resistance of modified asphalt, compare with NG, and AFM confirm that MG can obviously affect the rearrangement of four components in asphalt to form a micellar structure with higher modulus and lower energy dissipation. MD simulation further verifies that the higher mechanical strength of large-sized graphene modified asphalt is attributed to the reduced slide movement of cavitation structures in asphalt, since the larger graphene not only has stronger π-π interaction with asphaltene and resin, but also induces one more specific interaction of hydrogen bonds (O-H···S) between these polar components. The coupling interaction facilitates the formation of more compact micelles, resulting in the improved mechanical properties of asphalt. The elucidation of graphene size effect on asphalt provides encouragement for understanding the enhancement of graphene modified asphalt.
Novel composite ionic liquid and polyimide membranes with dissolved RuCl3 catalyst for H2/CO reactive separation were fabricated to combine gas diffusive separation and water-gas shift reaction. The ...CO concentration in the membranes is reduced via its reaction with H2O to form CO2 and H2, catalysed by the Ru carbonyl complex which forms in the reaction between dissolved RuCl3 and CO. In order to optimize the membrane configurations and operating conditions, water-gas shift reaction turnover frequencies (TOFs) of the membranes with various concentrations of ionic liquid and RuCl3 were determined at different pressures, temperatures and times-on-stream on a purpose-built test rig. The results show that the ionic liquid, C4mimOTf, improves TOFs by increasing the solubilities of H2O and the gases solubilities within the membrane. TOFs were found to increase initially, but reduce as time-on-stream increased, due to the formation and subsequent evaporation of a Ru carbonyl complex. Lower temperature and lower concentration of C4mimOTf were found to minimize the loss of the catalyst. It is suggested that the 2wt% RuCl3·xH2O+20wt% C4mimOTf+PI membrane operated at 140°C and 2bar has the best combination of reactivity and durability.
•Composite ionic liquid/polymer/catalyst membranes were fabricated.•Excellent mechanical and thermal stability over a wide range of conditions.•RuCl3 catalyst and C4mimOTf found to significantly enhance H2/CO separation.•Catalyst stabilized by operating at lower temperatures and pressures.•These composite membranes hold significant potential in fuel cell applications.
•A novel installation of ultrasound transducers in a minichannel heat sink is designed.•Studying mechanism of flow boiling heat transfer enhancement under ultrasound by high-speed visualization.•The ...maximum enhancement ratios is 53.9%.
The enhancement of the heat transfer assisted by ultrasound is considered to be an interesting and highly efficient cooling technology, but the investigation and application of ultrasound in minichannel heat sinks to strengthen the flow boiling heat transfer are very limited. Herein, a novel installation of ultrasound transducers in the flow direction of a minichannel heat sink is designed to experimentally study the characteristics of heat transfer in flow boiling and the influence of operation parameters (e.g., heat flux, mass flux rate) and ultrasound parameters (e.g., frequency, power) on the flow boiling heat transfer in a minichannel heat sink with and without ultrasound field. Bubble motion and flow pattern in the minichannel are analyzed by high-speed flow visualization, revealing that the ultrasound field induces more bubbles at the same observation position and a forward shift of the onset of nucleation boiling along the flow direction, as ultrasonic cavitation produces a large number of bubbles. Moreover, bubbles hitting the channel wall on the left and right sides are found, and the motion speed of the bubbles is increased by 31.9% under the ultrasound field. Our results demonstrate that the heat transfer coefficient obtained under the ultrasound field is 53.9% higher than in the absence of the ultrasound field under the same conditions, and the enhancement ratio is decreased in the high heat flux region due to the change of the flow regime with increasing heat flux. This study provides a theoretical basis for the application of an ultrasound field in minichannel heat sinks for the enhancement of flow boiling heat transfer.
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•3D porous graphene (3DPG) as reinforced additive was investigated in SBS/crumb rubber blend-modified asphalt.•3DPG can significantly improve high and low-temperature performance and ...fatigue life of SBS/crumb rubber blend-modified asphalts.•The nanopores in 3DPG can effectively enhance the compatibility of SBS and crumb rubber in asphalt system by virtue of its unique amphiphilicity.•3DPG as a new synergist presents a promising solution for the critical issue of wide adoption of crumb rubber modified asphalt for high-performance pavement.
Styrene-butadiene-styrene (SBS)/crumb rubber (CR) blend-modified asphalt is a desirable binder for pavement engineering with both environmental and economic benefits. However, the inherent incompatibility of SBS and CR in asphalt is still a critical issue. Herein, 3D porous graphene (3DPG) with high surface area and rich micropores as reinforced additive was investigated in SBS/CR blend-modified asphalt for the first time. The experimental results demonstrate that incorporating 3DPG can effectively improve the compatibility of SBS and CR in asphalt and thus significantly enhance the high and low temperature performance and fatigue resistance of the modified asphalt, compared with that without 3DPG. Theoretical calculations further reveal that the nanopores in graphene can endow graphene with electrophilic property, providing a capability of absorbing nonpolar molecules in asphalt while the non-pore part in graphene can interact with polar molecules by conventional π − π stacking. The two forces within graphene can break the original colloidal structures of asphalt, which is conductive to the homogenous formation of SBS network and swelling of CR in asphalt, significantly promoting the pavement performance of the modified asphalt. This work presents the great potential of 3DPG as new additive to solve the inherent incompatibility of SBS/CR blend-modified asphalt for high-grade pavement engineering.
The enhancement of the mechanical and wear-resistant properties of polymer coatings plays a vital role for their application in hostile serving environments, and nanofiller is effective for this ...purpose. Herein, we systematically investigate a new nanofiller, nitrogen-doped graphene sheets (NGSs), which possess a multilayer sheet-like morphology and share a good compatibility with water. After the incorporation of NGS into a waterborne polyurethane (WPU), the mechanical and wear-resistant properties of NGS/WPU composite coatings significantly improve, and wear resistance behaves best at an ultra-low content, reaching up to 0.005 wt% (50 ppm). Furthermore, Young’s modulus is elevated by 52.67% and tensile strength is appreciably boosted by 58.87%. Simultaneously, an apparent reduction of weight loss of 78.74% is observed in the abrasion testing, and the ductility of NGS/WPU composite films is reduced by 48.38%. These make it possible that an ultra-low content of nanofiller efficiently reinforces polymer-based composites, with low cost in the wear-resistance related field.
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It is critical to develop carbon material anodes with high initial Coulombic efficiency and energy density for sodium ion batteries. Herein, a novel mushroom spore with chitin as ...carbon precursor is first reported for energy storage, and its special porous spherical structure, fine structure and oxygen functional groups can be accurately controlled by carbonization temperature. The hollow porous carbon spheres obtained from mushroom spore at 1400 °C have appropriate porous structure, d002 spacing (0.364 nm), 7.12% oxygen content and ultra-low specific surface area of 5.5 m2 g−1. It could obtain 81.2% initial Coulombic efficiency and has reversible discharge capacity of 411.1 mA h g−1, wherein about 75% (308 mA h g−1) of its total capacity is derived from low-potential plateau (below 0.1 V Na+/Na), and the capacity is 384.5 mA h g−1 after 50 cycles. Furthermore, Density functional theory calculation showed that the residual oxygen functional groups (CO) in carbon materials are beneficial to sodium into graphite-like layers, and graphite-like layers spacing is smaller than the reported unadulterated carbon with 0.37 nm. Therefore, the excellent electrochemical performance and low-cost of natural mushroom spore derived hollow porous carbon spheres provide advantages for sodium ion batteries in large-scale storage devices.
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•A two-phase mass transfer model of paper-based microfluidic fuel cell is proposed.•The coupling characteristics of capillary action and two-phase flow are revealed.•The fluctuation ...mechanism of cell performance and gas distribution is explored.•Gas removal strategies are summarized, with a maximum gas removal rate of 42.30%.
Paper-based microfluidic fuel cell powered by capillary force has the advantages of compactness, low cost, and high sensitivity, presenting broad application prospects in portable electronic devices. However, the gas-liquid mass transfer mechanism within the porous medium remains unclear, with a lack of two-phase flow theories adapted to the unique paper-based system. In this study, a two-dimensional two-phase numerical model of a Y-shaped paper-based microfluidic fuel cell is developed to reveal the two-phase flow characteristics under capillary action and explore gas removal strategies. The reliability of the model is validated by real experimental data. By coupling multiple physical fields, the study elucidates the working principle and gas-liquid flow phenomena within the cell. Then, the effects of contact angle, inlet fuel concentration, and paper type on output performance, gas distribution, parasitic effect, and fuel utilization are discussed. The results indicate that increasing the contact angle and using paper with a larger average pore size and porosity as the channel substrate are ideal for promoting gas discharge. The optimal gas removal rate reached 42.30 %, with a favorable power density of 33.92 mW/cm2. This study provides a theoretical basis for a deeper understanding of the two-phase mass transfer process in paper-based microfluidic fuel cell.
•The mechanisms of various losses in microfluidic fuel cell are revealed.•Optimization strategies for enhancing electrocatalytic activity are summarized.•The optimization ideas of weakening ohmic ...polarization effect are determined.•A detailed review on alleviative concentration polarization is conducted.
The microfluidic fuel cell is one of the most promising micro power sources for the portable electronic devices due to the low cost, environmental friendliness, and substantial power outputs. The practical voltage output is lower than that of thermodynamic theory prediction because of the unavoidable losses in practice, and the polarisation losses are formed from the electrochemical loss, ohmic loss, and concentration loss. Abundant optimisation investigations are conducted in previous articles for decreasing the polarisation loss and improving the cell performance. Researches show that the exchange current density is increased and activation reaction energy barrier is decreased via the decoration and modification of catalytic electrode, thereby reducing the electrochemical loss. Improving the electric conduction via the setting of current collector can effectively reduce the ohmic loss. Moreover, the ohmic loss is decreased by using the high concentration electrolyte and reducing the ion transport distances between the anode and cathode. Optimising the channel and electrode structures including the development of novel structure, the setting of microridge, and array anode can availably limit the fuel concentration and depletion effect, thus decreasing the concentration loss. Significantly, the reduced concentration polarisation is realized by increasing flow rate and employing counter flow configuration.
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