Transport Resistance Research Articles

Three-dimensional allium flower-like iron-cobalt sulfide nanomaterials for high-performance supercapacitors

Supercapacitors with their improved performance in high energy density and long-term cycling stability have been the growing trend in recent years for fulfilling the demand of efficient energy storage systems. Herein, we report morphology-controlled three-dimensional (3D) Allium flower-like bimetallic iron-cobalt sulfide (3D-FeCoS AF) nanomaterials on nickel foam (NF) electrodes using a single-step electrochemical deposition strategy. The self-standing bimetallic 3D-FeCoS AF nanostructures show good performance towards the supercapacitance applications. The 3D-FeCoS AF nanostructures delivered a specific capacitance of ∼375.7 F g−1 at a current density of 1.0 A/g. The possible electron cloud delocalization among the FeS nanostructures through d-bands leads to the lower charge transport resistance at the 3D-FeCoS AF electrode–electrolyte interfaces and improved conductivity. The 3D-FeCoS AF electrode demonstrated excellent specific capacity and rate performance in a 2.0 M KOH electrolyte. Owing to their enormous electrochemical active surface area (ECSA) and distinctive 3D nanosheet morphology, the present 3D-FeCoS electrode holds great potential for the fabrication of additional transition metal sulfide materials for excellent supercapacitor performances. The findings of this study suggest promising prospects for the utilization of these materials in practical supercapacitance applications.

Highly efficient solar seawater evaporation by aerogel with vertical channels and hierarchical pores structure based on high-absorbent alginate fibers

Utilizing interfacial evaporation under sunlight is an effective way for desalination. Researchers have developed various solar evaporators to replace traditional processes. However, crystalline salt deposition and low evaporation rates have hindered the application of solar evaporators, which remain critical challenges in the field. Inspired by vascular plants, a novel strategy using natural high-absorbent alginate fibers as the aerogel backbone and polypyrrole as the solar absorber was employed to prepare an eco-friendly solar evaporator in this study. The biomimetic evaporator with abundant hydrophilic groups, vertical channels, and hierarchical pores structure inside achieves a maximum evaporation efficiency of 4.27 kg m-2h−1 under one solar intensity radiation, with an energy efficiency of more than 99 %. The nano polymer photo absorbents provide composite aerogels with excellent light absorption and mechanical properties, maintaining their shape and evaporation efficiency even after repeated use dozens of times. Its unique structures reduce water transport resistance radially to provide a fast water transport channel and efficiently desalinate, preventing salt from crystallizing on the evaporator surface. Obtaining a structurally controllable solar-driven evaporator in this way is expected to be used on a large scale for high-efficiency water purification, solving the freshwater resource crisis.

ZnO doped PAMAM for asphalt improvement as anti-corrosive coatings.

Asphalt is widely used as a coating resin due to its excellent adhesion strength and cost-effectiveness; however, its limited corrosion protection necessitates enhancement. In this study, poly(amidoamine) (PAMAM), combined with zinc oxide (ZnO) nanoparticles, was incorporated into the asphalt matrix to improve its anticorrosive properties. Various ratios of PAMAM-ZnO nanocomposite (1, 2, 4, and 6% by weight) were added to the asphalt binder, with the materials characterized using XRD, ¹H-NMR, and SEM techniques. The 2% PAMAM-ZnO/asphalt ratio exhibited the most significant improvement, achieving a corrosion protection efficiency (η%) of 97.93%, as confirmed by Tafel analysis, and a charge transport resistance (RCT) of 75.91 Ω cm² according to electrochemical impedance spectroscopy (EIS) data. A combination of barrier formation and sacrificial protection drives the corrosion inhibition mechanism. The PAMAM-ZnO nanocomposite forms a highly uniform layer on the carbon steel surface, creating an effective physical barrier that prevents the penetration of corrosive agents, thereby minimizing defects like pinholes. This barrier effect is complemented by the sacrificial protection provided by the ZnO nanoparticles, which are more reactive than the underlying steel and preferentially interact with corrosive ions (e.g., chloride ions). This interaction leads to the formation of stable ZnO corrosion products, which enhance the barrier and reduce the likelihood of corrosion on the steel surface. Additionally, PAMAM facilitates the even distribution and strong adhesion of ZnO within the asphalt matrix, ensuring a durable protective layer. The synergic impact between the polymer barrier and sacrificial ZnO protection results in the exceptional corrosion resistance observed in the 2% PAMAM-ZnO/asphalt formulation, offering a promising approach for advanced anticorrosive coatings.

Fe‐N‐C in Proton Exchange Membrane Fuel Cells: Impact of Ionomer Loading on Degradation and Stability

AbstractFe single atoms in N‐doped C (Fe‐N‐C) present the most promising replacement for carbon‐supported Pt‐based catalysts for the O2 reduction reaction at the cathode of proton exchange membrane fuel cells (PEMFCs). However, it remains unclear how the I/C ratio affects Fe‐N‐C degradation and the stability of single Fe atom active sites (FeNx). Here, an accelerated stress test (AST) protocol is combined with emerging electrochemical techniques for a porous Fe‐N‐C in PEMFC with a range of I/C ratios. The PEMFC current density degradation rates are found to be comparable; however, with increased I/C ratio the additional FeNx sites accessed are more stable, as shown by their higher active site stability number (electrons passed per FeNx lost) at the end of the AST protocol. Meanwhile, the initial rate of TOF decay is suppressed with increasing I/C. Electrochemical process changes are studied via distribution of relaxation times analysis. Minor changes in H+ and O2 transport resistance at low current density prove kinetic degradation dominants at high potentials. These findings demonstrate how electrochemical techniques can be combined with stability metrics to determine and deconvolute changes from the active site to device level electrochemical processes in PEMFCs.

Variation of six local poplar clones in growth and eco-physiological traits in two types of arid valleys

Abstract Six clones of native poplars were used in a field trial to investigate variations in survival, growth, and adaptation to arid-warm and arid-hot valleys. In the arid-hot valley, clone Y1-2 exhibited the highest survival rate and growth condition, surpassing other clones, while clones B7-4 and P3-6 demonstrated superior survival and growth performance in the arid-warm valley. Clone B7-4 displayed the highest soluble sugar content in leaves across both habitats. SOD and APX activities, along with MDA content in leaves, were higher in the arid-hot valley for all clones compared to the arid-warm valley. Long-term water use efficiency, as indicated by δ13C in leaves, was significantly higher for all clones in the arid-hot valley, particularly for H1-6, T3-2, and P3-6. Increases in upper epidermis thickness were observed in clones E1, B7-4, and P3-6, while Y1-2 exhibited a higher palisade parenchyma thickness (PT) in the arid-hot valley compared to the arid-warm valley. Vein densities were higher in leaves of clones E-1, B7-4, Y1-2, and P3-6 in both valleys compared to other clones, with B7-4 showing a significant increase in mean vein width in the arid-hot valley. In conclusion, the superior growth performance of clone B7-4 in the arid-warm valley may be attributed to its stronger osmotic adjustment and higher capacity to maintain water transportation through venation. The exceptional performance of clone Y1-2 in the arid-hot valley may be associated with its compact arrangement of PT, as well as its stronger capacity for hydraulic transport and antioxidant resistance in leaves.

Effect of substrate type on structural and electrochemical performance of vertical graphene nanosheets deposited by HWP-CVD

Vertical graphene nanosheets (VGs) were synthesized on Cu, Ti, Si, and C substrates by helicon wave plasma chemical vapor deposition (HWP-CVD) method using CH4/Ar as precursors. The obtained samples formed vertical orientation structures of nanosheets-graphene as the scanning electron microscopy and TEM images indicated. Specifically, the VGs grown on Cu substrate exhibit a parallel arrangement with a wall spacing of approximately 450 nm. This structural characteristic facilitates efficient ion exchange channels and promotes low resistance for electron transport. The effect of substrate type on the growth mechanism of VGs was discussed. The relationship between the microstructure and electrochemical performance of the VGs grown on different substrates was investigated. The charge transfer resistance of the VGs/Cu is 20.75 Ω, and the value of VGs/Ti, VGs/C and VGs/Si are 23.51 Ω, 33.76 Ω and 66.40 Ω, respectively. The robust vertical orientation structure of VGs holds promise for various applications, including catalyst support in fuel cells, conductive electrodes in photovoltaic cells, and energy storage devices like lithium-ion batteries and supercapacitors. This structural characteristic plays a pivotal role in advancing the development of next-generation energy storage technologies.

The effect of gelatinized brown rice extract on type 2 diabetes mellitus via inhibition of insulin resistance mediators in HepG2 cells

The purpose of this study evaluated effects of gelatinized brown rice extract (GBE) on type 2 diabetes mellitus by analyzing antioxidant activity, polysaccharide-degrading enzymes activity, and regulation of insulin secretion and glucose transport-related factors in human liver cells (HepG2). Quantified polyphenols and flavonoids in extract showed 6.7 mg gallic acid equivalent/g dry matter (DM) and 5.3 mg quercetin equivalent/g DM, respectively, with DPPH and ABTS radical scavenging activities confirmed to 67.1 ~ 77.7%. Additionally, extract inhibited alpha-glucosidase activity by 81.9%, thereby demonstrating potential for improving blood glucose regulation. To demonstrate alleviation of type 2 diabetes through mitigation of insulin resistance and promotion of glucose transport, expression of genes related to insulin receptor genes (Insulin Receptor Substrate-1, Protein Kinase B) increased by 18.5 ~ 28.3%, while expression of counterregulatory hormone genes (Insulin-like Growth Factor-1) decreased by 33.3%. Additionally, expression of glucose transporter proteins (Glucose Transporter Type-4, 2) increased by 30.9 ~ 42.0%, and expression of proteins that reduce insulin sensitivity (Insulin Receptor Substrate-2) decreased by 34.6%. These results indicated that insulin resistance in hepatocytes alleviated, and glucose transport promoted, leading to decreased blood glucose levels.

MgAl-Layered Double Hydroxide-Coated Bio-Silica as an Adsorbent for Anionic Pollutants Removal: A Case Study of the Implementation of Sustainable Technologies.

The adsorption efficiency of Cr(VI) and anionic textile dyes onto MgAl-layered double hydroxides (LDHs) and MgAl-LDH coated on bio-silica (b-SiO2) nanoparticles (MgAl-LDH@SiO2) derived from waste rice husks was studied in this work. The material was characterized using field-emission scanning electron microscopy (FE-SEM/EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopic (XPS) techniques. The adsorption capacities of MgAl-LDH@SiO2 were increased by 12.2%, 11.7%, 10.6%, and 10.0% in the processes of Cr(VI), Acid Blue 225 (AB-225), Acid Violet 109 (AV-109), and Acid Green 40 (AG-40) dye removal versus MgAl-LDH. The obtained results indicated the contribution of b-SiO2 to the development of active surface functionalities of MgAl-LDH. A kinetic study indicated lower intraparticle diffusional transport resistance. Physisorption is the dominant mechanism for dye removal, while surface complexation dominates in the processes of Cr(VI) removal. The disposal of effluent water after five adsorption/desorption cycles was attained using enzymatic decolorization, photocatalytic degradation of the dyes, and chromate reduction, satisfying the prescribed national legislation. Under optimal conditions and using immobilized horseradish peroxidase (HRP), efficient decolorization of effluent solutions containing AB-225 and AV-109 dyes was achieved. Exhausted MgAl-LDH@SiO2 was processed by dissolution/precipitation of Mg and Al hydroxides, while residual silica was used as a reinforcing filler in polyester composites. The fire-proofing properties of composites with Mg and Al hydroxides were also improved, which provides a closed loop with zero waste generation. The development of wastewater treatment technologies and the production of potentially marketable composites led to the successful achievement of both low environmental impacts and circular economy implementation.

Atomistic insights into the K+/Na+ separation across amino modified graphene nanopore: The assisting role of Cl−

K+/Na+ separation has always been considered the most challenging. We adopted molecular dynamics to compare graphene nanopores modified with positively charged amino groups and their pristine counterparts to unravel the mechanism underlying the effect of positively charged amino groups on K+/Na+ separation and evaluate the assisting effect of Cl−. Two pore diameters of approximately 1 nm were selected. Results demonstrated that nanopore modification can effectively improve the K+/Na+ selectivity, and the spatial distribution and residence time of Cl− near the nanopores indicated that modification with positively charged amino groups can induce the dynamical adsorption of Cl− around the nanopores. In the studied nanopores, the prolongation of the residence time of Cl− at the pore mouths can increase the difference between K+ and Na+ dehydration and thus can increase their transport resistance difference. The latter effect is conducive to improving the selectivity for K+. Our findings can provide useful insight for the further design of K+ separating two-dimensional materials as sensors and ion separators.

Spatial‐Dependent Coupling of Electrochemistry, Mass Transport, and Stress in Silicon‐Graphite Composite Electrodes for Lithium‐Ion Batteries

AbstractThe commercialization of high‐capacity silicon materials in lithium‐ion batteries is hindered by significant volume changes. Composite anodes made from silicon and graphite, which increase battery capacity and maintain electrode structural stability, are receiving considerable attention. However, the spatial configuration of the active particles in the electrode is few investigated due to the complexity of experiments at the microscopic scale. Herein, this work focuses on electrochemical, mass transport, and stress coupling mechanisms by considering different spatial configurations of silicon and graphite. In situ electrochemical and stress measurements are first conducted to demonstrate the impact of the active material arrangement. Then, a 2D electrochemical‐mechanical model is developed considering the heterogeneity of electrochemical processes at the particle‐electrolyte interface. The results show that placing silicon in the upper active layer significantly reduces the ion transport resistance, while the graphite layer near the current collector provides a good conductive network for electron transport in the silicon layer, enhancing the performance of the composite electrode structure. By combining electrochemical and mechanical field models with experimental verification, this study deepens the understanding of composite electrode structure design, offering practical guidance for optimizing the spatial configuration of electrode materials to significantly improve battery performance.

Structure and function of Mycobacterium tuberculosis EfpA as a lipid transporter and its inhibition by BRD-8000.3

EfpA, the first major facilitator superfamily (MFS) protein identified in Mycobacterium tuberculosis (Mtb), is an essential efflux pump implicated in resistance to multiple drugs. EfpA-inhibitors have been developed to kill drug-tolerant Mtb. However, the biological function of EfpA has not yet been elucidated. Here, we present the cryo-EM structures of EfpA complexed with lipids or the inhibitor BRD-8000.3 at resolutions of 2.9 Å and 3.4 Å, respectively. Unexpectedly, EfpA forms an antiparallel dimer. Functional studies reveal that EfpA is a lipid transporter and BRD-8000.3 inhibits its lipid transport activity. Intriguingly, the mutation V319F, known to confer resistance to BRD-8000.3, alters the expression level and oligomeric state of EfpA. Based on our results and the observation of other antiparallel dimers in the MFS family, we propose an antiparallel-function model of EfpA. Collectively, our work provides structural and functional insights into EfpA's role in lipid transport and drug resistance, which would accelerate the development of antibiotics against this promising drug target.

Overcoming the Limitation of Ionomers on Mass Transport and Pt Activity to Achieve High-Performing Membrane Electrode Assembly.

The membrane electrode assembly (MEA) is one of the critical components in proton exchange membrane fuel cells (PEMFCs). However, the conventional MEA cathode with a covered-type catalyst/ionomer interfacial structure severely limits oxygen transport efficiency and Pt activity, hardly achieving the theoretical performance upper bound of PEMFCs. Here, we design a noncovered catalyst/ionomer interfacial structure with low proton transport resistance and high oxygen transport efficiency in the cathode catalyst layer (CL). This noncovered interfacial structure employs the ionomer cross-linked carbon particles as long-range and fast proton transport channels and prevents the ionomer from directly covering the Pt/C catalyst surface in the CL, freeing the oxygen diffusion process from passing through the dense ionomer covering layer to the Pt surface. Moreover, the structure improves oxygen transport within the pores of the CL and achieves more than 20% lower pressure-independent oxygen transport resistance compared to the covered-type structure. Fuel-cell diagnostics demonstrate that the noncovered catalyst/ionomer interfacial structure provides exceptional fuel-cell performance across the kinetic and mass transport-limited regions, with 77% and 67% higher peak power density than the covered-type interfacial structure under 0 kPagauge of oxygen and air conditions, respectively. This alternative interfacial structure provides a new direction for optimizing the electrode structure and improving mass-transport paths of MEA.

Enhanced Photovoltaic Performance of Poly(3,4-Ethylenedioxythiophene)Poly(N-Alkylcarbazole) Copolymer-Based Counter Electrode in Dye-Sensitized Solar Cells

Conducting polymers are emerging as promising alternatives to rare and expensive platinum for counter electrodes in dye-sensitized solar cells; due to their ease of synthesis, they can be chemically tuned and are suitable for roll-to-roll production. Among these, poly (3,4-ethylenedioxythiophene) (PEDOT)-based counter electrodes have shown leading photovoltaic performance. However, certain conductivity issues remain that affect the effectiveness of these counter electrodes. In this study, we present an electropolymerized PEDOT and poly(N-alkylated-carbazole) copolymer as an efficient electrocatalyst for the reduction in I3− in dye-sensitized solar cells. Copolymerization with N-alkylated carbazoles significantly increases the conductivity of the polymer film and facilitates rapid charge transport at the interface between the polymer electrode and the electrolyte. The length of the alkyl substituents also plays a crucial role in this improvement. Electrochemical analysis showed a reduction in charge transport resistance from 3.31 Ω·cm2 for PEDOT to 2.26 Ω·cm2 for the PEDOT:poly(N-octylcarbazole) copolymer, which is almost half the resistance of a platinum-based counter electrode (4.12 Ω·cm2). Photovoltaic measurements showed that the solar cell with the PEDOT:poly(N-octylcarbazole) counter electrode achieved an efficiency of 8.88%, outperforming both PEDOT (7.90%) and platinum-based devices (7.57%).

Humidity-Induced Degradation Mapping of Pt3Co ORR Catalyst for PEFC by In-Operando Electrochemistry and Ex Situ SAXS.

Understanding the degradation mechanisms of Pt-alloy catalysts is crucial for enhancing their durability. This study investigates the impact of relative humidity on Pt and Pt3Co catalysts using potential-cycling-based accelerated stress tests. Two conditions are investigated: 100% relative humidity on both sides, and a gradient with 30% at the anode and over 100% at the cathode. Pt3Co demonstrates sensitivity, with 77% performance loss and reductions in electrocatalyst surface area. Results demonstrate a 30% decrease in potential loss for Pt catalysts and a 77% increase for Pt3Co catalysts, indicating significant performance degradation in high humidity conditions, with Pt3Co exhibiting greater sensitivity. Measurements of electrochemically active surface area reinforce these findings. Resistance analysis using electrochemical impedance spectroscopy using equivalent circuit modeling reveals a threefold increase in Pt3Co MEAs' cathode charge transfer resistance and mass transport resistance during accelerated stress tests. Local current distribution analysis highlights differences between Pt catalyst and Pt3Co, with the latter displaying dealloying effects. Small-angle X-ray scattering reveals changes in particle and cluster sizes, indicating structural changes. Scanning electron microscopy highlights catalyst and membrane thickness variations, suggesting heterogeneity in Pt3Co. Under humidity gradients, Ostwald ripening plays a significant role in altering the catalyst's Pt3Co structure and subsequently impacting its performance.

Poly(aniline)-multiwall carbon nanotube (PANI@MWCNT) composite as high-cost Pt free counter electrode for dye-sensitized solar cells

In this study, we synthesized a poly (aniline)-multiwall carbon nanotube (PANI@MWCNT) composite for use as a counter electrode (CE) in dye-sensitized solar cells. Moreover, FE-SEM and HR-TEM images of PANI@MWCNT revealed carbon nanotube/ropes embedded in the polymer matrix. An X-ray diffraction pattern confirmed the amorphous nature of the composite. Further, Electrochemical impedance spectroscopy studies indicated a charge transport resistance value (Rct) of 4.36 KΩ for PANI@MWCNT. CV studies demonstrated improved electrocatalytic performance and faster redox behavior in the PANI@MWCNT composite. BET analysis measured the pore size of the as-prepared composite to be 15–50 nm. Subsequently, the as-synthesized PANI, PANT@MWNCT, pristine MWCNT, and platinum were evaluated as CEs in DSSCs using a polyethylene oxide polymer-based liquid electrolyte and a TiO2 nanocrystalline photoanode. Among these CEs, the PANI@MWCNT CE exhibited an efficiency of 8.07 %, and the stability test indicated that the as-prepared composite CE retained 7.81 % efficiency after 15 days.

Effect of High-Temperature Operation on Voltage Cycling Induced PEMFC Degradation: From Automotive Customer Drive Cycles to an Accelerated Stress Test

Degradation of the Pt catalyst during load cycling constitutes a major durability issue for proton exchange membrane fuel cells (PEMFCs) in automotive applications. In this study commercial 5 cm2 electrodes were exposed to 20 k voltage cycles between 0.6–0.9 VRHE at temperatures ranging from 75 to 120 °C. The electrochemical surface area (ECSA), the roughness factor (rf), and the oxygen transport resistance were investigated over the course of the test. The degradation was mainly governed by Pt agglomeration and was accelerated with increasing temperature. Interestingly, operation at high temperature (120 °C and 30% RH) caused the same ECSA loss as at standard conditions (90 °C and 90% RH), suggesting that when maintaining dry conditions high-temperature operation is not critical for the durability of the catalyst material. The experimental results were used to validate an existing 0D catalyst degradation model, which was then applied to an automotive customer drive cycle. The calculated degradation over the whole automotive lifetime (excluding startup shutdown and idle events) equals 20 k voltage cycles (0.6–0.9 V, 10 s hold time) at 90 °C and 30% RH, which provides a guideline for the assessment of the suitability of novel catalyst materials for automotive applications.

CPAM-assisted synthesis of NaA zeolite membrane on macroporous mullite hollow fiber for ethanol dehydration by pervaporation

Due to the low transport resistance, mullite hollow fiber (HF) could be regarded as a promising support for preparation of NaA zeolite membranes. However, insufficient coverage and undesired seed penetration often occur in the seeding step of the mullite support due to the rough surfaces with ultra-large macropores (2–4 μm). This leads to poor intergrowth of the membrane layer. To solve this issue, cationic polyacrylamide (CPAM) was employed to modify the chemical and electrostatic properties of the mullite HF surface, where the electrostatic attraction between the surface and seed crystals could significantly promote the coating effect. In the seeding, the original seeds (3.2 μm) were mixed with the ball-milled seeds (0.3 μm) to improve the seed coverage, i.e., the original seed was used to block the macropores on the support surface to prevent the penetration of small seeds, while the decked ball-milled seed was used to provide sufficient active sites to induce the intergrowth of the zeolite crystals. The effects of the concentration of CPAM, mixed mass ratio of seeds, and seed concentration on the preparation of NaA zeolite membranes were systematically examined, where the separation performances were characterized by pervaporation (PV) dehydration of 90% (mass) ethanol/water mixtures at 75 °C. The results indicated that under a CPAM concentration of 0.7% (mass), an equivalent mass ratio of mixed seeds in a seed concentration of 1.0% (mass), the prepared mullite HF supported NaA zeolite membrane yielded the best PV performance, where the permeation flux and separation factor corresponded to 5.45 kg·m−2·h−1 and 10000, respectively, being sufficient for industrial applications.

High protonic resistance of hydrocarbon-based cathodes in PEM fuel cells under low humidity conditions: Origin, implication, and mitigation

Hydrocarbon-based electrodes for proton-exchange membrane fuel cells face challenges in closing the performance gap with electrodes based on perfluorosulfonic acid ionomers, particularly under low humidity conditions. Alongside increased oxygen transport resistance and higher kinetic-induced overpotentials, the protonic resistance of these fluorine-free electrodes is the primary hurdle to improved performance. This study systematically investigates the origin and impact of the cathode protonic resistance on fuel cell performance, utilizing sulfonated phenylated polyphenylenes as hydrocarbon ionomers. Electrochemical characterization at low relative humidity (≤50 %) reveal a high protonic resistance arising from both lower conductivity of the hydrocarbon thin film compared to the bulk membrane and increased cathode tortuosity at a gas transport-optimized ionomer to carbon (I/C) ratio of 0.2. The poor protonic resistance at low relative humidities leads to a non-homogeneous current distribution across the thickness of the cathode electrode, resulting in lower catalyst utilization. To address this issue, reducing the thickness of the cathode CL while maintaining a constant Pt loading (i.e., increasing the Pt on carbon ratio) significantly reduces protonic resistance. This improvement compensates for the kinetic disadvantages of highly loaded carbon particles and results in a considerable performance increase by 40 % at 0.75 V under low relative humidities.

Honeycomb ZIF-67 Membrane With Hierarchical Channels for High-Permeance Gas Separation.

Membrane technology exhibits low cost and high efficiency in gas separation. Zeolite-imidazole framework-67 (ZIF-67) membrane shows a theoretically superior performance in H2/CO2 separation, owing to its effective size-sieving pores between H2 and CO2. However, the gas molecules are permeate through a series of consecutive crystal cells of common ZIF-67 polycrystalline membranes, resulting in high transport resistance to the gas permselective transport. To this end, this work employs a contra-diffusion synthesis to construct a honeycomb ZIF-67 (h-ZIF67) crystalline membrane for low-resistance H2/CO2 permselective transport. The controlled growth of h-ZIF67 following the van der Drift theory produces the honeycomb polycrystal with hierarchical channels for low-resistance gas permeation. The prepared membrane with micron-scale thickness still achieves a H2 permeance as high as 1.6 × 10-7molm-2s-1Pa-1 and a H2/CO2 selectivity of 17, which can be maintained after a long-term operation for the H2/CO2 mixture separation.

Influence of the Clamping Force and the Formation of Liquid Water Along the Channel on the Local Diffusion Processes in PEMFCs

A novel measurement setup, technique, and segmented model are introduced to spatially resolve mass transport losses along the channel in a PEMFC. The newly designed segmented cell enables not only the measurement of local current and voltage data but also the capture of local temperature and compression levels. By extending the commonly used limiting current method, the local mass transport resistance is determined as a function of local operating parameters. The local current and temperature are directly measured, while the operating conditions along the channel such as pressure, oxygen fraction, and relative humidity are obtained empirically from a 1-D differential model. Leveraging both measured and empirically-based simulation results, this comprehensive approach facilitates the characterization of mass transport resistance distribution along the gas channel. The learnings from this study provide valuable insight into the optimization of channel and materials design for enhancing large active area fuel cell performance and durability.