Membrane Layer Research Articles

The Technical and Industrial Challenges Faced by Fuel Cells—A Case Study of PEMFC And SOFC

Fuel cells are a proficient and environmental technology that directly transmutes chemical energy into electrical energy. Within this domain, Proton Exchange Membrane Fuel Cells (PEMFCs) and Solid Oxide Fuel Cells (SOFCs) are at the forefront of small-scale applications and industrial power generation, respectively. The efficacy and economic feasibility of PEMFCs are contingent upon key components, such as the proton exchange membrane and mass transport layers. Consequently, contemporary research is geared towards the optimization of these components to augment performance while concurrently mitigating costs. Conversely, the operational capacity of SOFCs at elevated temperatures has spurred research efforts aimed at material enhancement and the diversification of applications. These advancements encompass the integration of additives, the exploration of novel membrane fabrication methodologies, and the development of innovative structural designs for fuel cells. Although there have been progressive strides in the realm of hydrogen-powered vehicles and fuel cell power plants, their assimilation into the market has been somewhat languid, with commercialization still facing a myriad of challenges. Notwithstanding these hurdles, it is anticipated that with the ongoing evolution of technology and a concomitant reduction in costs, fuel cells will persist as a pivotal component in the quest for energy cleanliness and efficiency.

Potential-Dependent Ionomer Rearrangement on the Pt Surface in Polymer Electrolyte Membrane Fuel Cells.

The interface between the catalyst and the ionomer in the catalyst layer of polymer electrolyte membrane fuel cells (PEMFCs) has been a subject of keen interest, but its effect on durability has not been fully understood due to the complexity of the catalyst layer structure. Herein, we utilize a Pt nanoparticle (NP) array electrode fabricated using a block copolymer template as the platform for a focused investigation of the interfacial change between the Nafion thin film and the Pt NP under a constant potential. A set of analyses for the electrodes treated with various potentials reveals that the Nafion thin film becomes densely packed at the intermediate potentials (0.4 and 0.7 V), indicating an increased ionomer-catalyst interaction due to the positive charges formed at the Pt surface at these potentials. Even for a practical PEMFC single cell, we demonstrate that the potential holding at the intermediate potentials increases ionomer adsorption to the Pt surface and the oxygen transport resistance, negatively impacting its power performance. This work provides fresh insight into the mechanism behind the performance fade in PEMFCs caused by potential-dependent ionomer rearrangement.

Effect of polytetrafluoroethylene shedding on water and heat transport in the gas diffusion layer of proton exchange membrane fuel cells

Effect of polytetrafluoroethylene shedding on water and heat transport in the gas diffusion layer of proton exchange membrane fuel cells

Preparation of highly selective nanofiltration composite membranes based on a novel soluble rigidly contorted monomer

AbstractNanofiltration composite membranes with high selectivity are one of the most critical cores in water treatment, and regulating the surface charge and pore structure of active separation layers in thin film composite membranes is one of the most effective means to improve the selectivity of composite membranes. This article synthesized a novel monomer with positive charge and a rigid twisted Tröger's base structure (named TBDA‐SO3), which was manipulated to improve the microporous structure and surface charge of the composite membrane. By interfacial polymerization, TBDA‐SO3, and piperazine were co‐reacted with trimesoyl chloride to successfully prepare positively charged, highly selective, and strongly microporous polyamide composite nanofiltration membranes. The best‐performing composite nanofiltration membrane in this article has a permeability similar to that of the control group's poly(piperazine amide) (PPA) membrane (pure water flux, 7.8 L m−2 h−1 bar−1), but has excellent divalent cation selectivity (52.57), which is 4.4 times that of the control group's PPA membrane.

Multi-objective optimization of ice distribution uniformity and startup failure time for cold start of PEMFC catalyst layer based on CTnet and PSO-GA

The distribution of ice in the cathode catalyst layer (CCL) of a proton exchange membrane fuel cell (PEMFC) has a significant impact on cold start. A three-dimensional multiphase numerical model for fuel cell cold start was developed to investigate the first-order finite difference sensitivities of seven selected parameters, namely gas diffusion layer (GDL) porosity, CCL porosity, ionomer volume fraction, inlet temperature, initial membrane water content, catalyst layer (CL) surface area, and initial current, with respect to the uniformity of ice distribution and cold start failure time. Six of these parameters were chosen as inputs for a CNN-Transformers based neural network (CTnet), which was developed using Convolutional Neural Networks (CNN) and the multi-head attention mechanism of Transformers as a surrogate model for cold start. The optimization algorithm PSO-GA was used to find the optimal operating and geometric parameters, aiming to achieve the most uniform ice distribution in the CCL and extend the final cold start failure time. The optimized ice distribution uniformity was found to be 0.204446, showing a 1.1163 % improvement compared to the baseline model. The final cold start failure time was extended by 15.625 % to 185 s compared to the baseline model. The optimized model exhibited a more uniform distribution of ice during cold start, resulting in an extended cold start failure time. This indicates a reduced performance impact on the CCL, thereby improving the durability of the fuel cell. The optimization provides additional time for future auxiliary cold starts, while also enhancing the starting speed of auxiliary cold start through improved ice distribution uniformity.

The biomechanical effects of different membrane layer structures and material constitutive modeling on patient-specific cerebral aneurysms.

The prevention, control and treatment of cerebral aneurysm (CA) has become a common concern of human society, and by simulating the biomechanical environment of CA using finite element analysis (FEA), the risk of aneurysm rupture can be predicted and evaluated. The target models of the current study are mainly idealized single-layer linear elastic cerebral aneurysm models, which do not take into account the effects of the vessel wall structure, material constitution, and structure of the real CA model on the mechanical parameters. This study proposes a reconstruction method for patient-specific trilaminar CA structural modeling. Using two-way fluid-structure interaction (FSI), we comparatively analyzed the effects of the differences between linear and hyperelastic materials and three-layer and single-layer membrane structures on various hemodynamic parameters of the CA model. It was found that the numerical effects of the different CA membrane structures and material constitution on the stresses and wall deformations were obvious, but does not affect the change in its distribution pattern and had little effect on the blood flow patterns. For the same material constitution, the stress of the three-layer membrane structure were more than 10.1% larger than that of the single-layer membrane structure. For the same membrane structure, the stress of the hyperelastic material were more than 5.4% larger than that of the linear elastic material, and the displacement of the hyperelastic material is smaller than that of the linear elastic material by about 20%. And the maximum value of stress occurred in the media, and the maximum displacement occurred in the intima. In addition, the upper region of the tumor is the maximum rupture risk region for CA, and the neck of the tumor and the bifurcation of the artery are also the sub-rupture risk regions to focus on. This study can provide data support for the selection of model materials for CA simulation and analysis, as well as a theoretical basis for clinical studies and subsequent research methods.

Determining Susceptibility and Potential Mediators of Resistance for the Novel Polymyxin Derivative, SPR206, in Acinetobacter baumannii.

With the increase in carbapenem-resistant A. baumannii (CRAB) infections, there has been a resurgence in the use of polymyxins, specifically colistin (COL). Since the reintroduction of COL-based regimens in treating CRAB infections, several COL-resistant A. baumannii isolates have been identified, with the mechanism of resistance heavily linked with the loss of the lipopolysaccharide (LPS) layer of the bacterial outer membrane through mutations in lpxACD genes or the pmrCAB operon. SPR206, a novel polymyxin derivative, has exhibited robust activity against multidrug-resistant (MDR) A. baumannii. However, there is a dearth of knowledge regarding its efficacy in comparison with other A. baumannii-active therapeutics and whether traditional polymyxin (COL) mediators of A. baumannii resistance also translate to reduced SPR206 activity. Here, we conducted susceptibility testing using broth microdilution on 30 A. baumannii isolates (17 COL-resistant and 27 CRAB), selected 14 COL-resistant isolates for genomic sequencing analysis, and performed time-kill analyses on four COL-resistant isolates. In susceptibility testing, SPR206 demonstrated a lower range of minimum inhibitory concentrations (MICs) compared with COL, with a four-fold difference observed in MIC50 values. Mutations in lpxACD and/or pmrA and pmrB genes were detected in each of the 14 COL-resistant isolates; however, SPR206 maintained MICs ≤ 2 mg/L for 9/14 (64%) of the isolates. Finally, SPR206-based combination regimens exhibited increased synergistic and bactericidal activity compared with COL-based combination regimens irrespective of the multiple resistance genes detected. The results of this study highlight the potential utility of SPR206 in the treatment of COL-resistant A. baumannii infections.

One-step fabrication of asymmetric alumina ceramic membranes with tunable pore parameters for oil-water separation

Porous ceramic membranes with low-cost and high performance are desirable in industrial filtration field. To improve the performance while reducing the production cost, various measures were developed, however, pre-sintering of supports, preparation of membrane-forming suspensions and adoption of extensive organic additives that involved were adverse to cost reduction. Herein, cost-effective one-step co-pressing and co-sintering technique was proposed to prepare asymmetric ceramic membranes. The results revealed that pore parameters and performance of the fabricated membranes could be adjusted by altering mole ratio of Al2O3 to SiO2 (Al2O3/SiO2) in the support and sintering temperature. The influence of supports on the permeation flux of membranes surpassed that of the parameters of membrane layer. Additionally, the oil rejection rate of the membranes exceeded 96 % within 2 min and even reached 100 % (~60 min), the water flux and steady-state feed flux were 1330–1730 L·m−2·h−1 and 470–620 L·m−2·h−1 at 1 bar, respectively. Moreover, cake filtration was the main fouling mechanism throughout the separation process. This research provides a feasible and simple method for preparing low-cost high-performance ceramic membrane for wastewater treatment.

Bottom-up approach to explore alpha-amylase assisted membrane remodelling

Soluble alpha-amylases play an important role in the catabolism of polysaccharides. In this work, we show that the malt α -amylase can interact with the lipid membrane and further alter its mechanical properties. Vesicle fluctuation spectroscopy is used for quantitative measurement of the membrane bending rigidity of phosphatidylcholines lipid vesicles from the shape fluctuation based on the whole contour of Giant Unilamellar Vesicles (GUVs). The bending rigidity of the 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine lipid vesicles in water increases significantly with the presence of 0.14 micromolar alpha-amylase (AA) in the exterior solution. It appears that the enzyme present in the external solution interacts with the outer layer of the bilayer membrane, leading to an asymmetry of the solution on either side of the bilayer membrane and altering its elasticity. At AA concentration of 1.5 micromolars and above, changes in the morphology of the GUV membrane are observed. The interaction between AA in the external solution and the external leaflet causes the bilayer membrane to curve spontaneously, leading to the formation of outbuds, giving a positive spontaneous curvature of C0 ≤ 0.05 μm−1 at ≈ 1 mg / ml of the AA concentration. We validate and characterize its concentration-dependent role in stabilizing the membrane curvature. Our findings indicate that the involvement of the enzyme, depending on the concentration, can have a considerable effect on the mechanical characteristics of the membrane.

Biomimetic ROS-responsive hyaluronic acid nanoparticles loaded with methotrexate for targeted anti-atherosclerosis.

Atherosclerosis (AS), an inflammatory disease characterized by lipid accumulation, has a high global incidence and mortality rate. Recently, nanotherapeutic approaches that target pathological sites and improve drug bioavailability and biocompatibility hold great promise for AS treatment. In this study, a biomimetic ROS-responsive hyaluronic acid-based nanomaterial was prepared for targeted anti-AS. Specifically, a safe ROS-responsive carrier based on hyaluronic acid (HSP) was prepared to load methotrexate (MTX), a drug known for its ability to enhance lipid excretion, resulting in the formation of MTX-loaded nanoparticles (MTXNPs). Furthermore, the macrophage membrane was coated on the surface of MTXNPs to obtain MM/MTXNPs. Both MTXNPs and MM/MTXNPs exhibited ROS responsiveness and demonstrated excellent biocompatibility. In vitro experiments revealed that MM/MTXNPs could evade macrophage phagocytosis and exhibited high uptake rates by inflamed endothelial cells. MM/MTXNPs also reduced lipid accumulation in foam cells. In vivo experiments showed that MM/MTXNPs exhibited superior accumulation at AS plaque sites, facilitated by the surface membrane layer containing integrin α4β1 and CD47, resulting in an enhanced therapeutic effect in inhibiting plaque development compared to free MTX and MTXNPs. Therefore, HSP represents a promising nanocarrier to load hydrophobic MTX, enabling effective and biocompatible enhancement of AS treatment.

Cytofluorometric assessment of calreticulin exposure on CD38+ plasma cells from the human bone marrow.

Exposure of the endoplasmic reticulum chaperone calreticulin (CALR) on the surface of stressed and dying cells is paramount for their effective engulfment by professional antigen-presenting cells such as dendritic cells (DCs). Importantly, this is required (but not sufficient) for DCs to initiate an adaptive immune response that culminates with an effector phase as well as with the establishment of immunological memory. Conversely, the early exposure of phosphatidylserine (PS) on the outer layer of the plasma membrane is generally associated with the rapid engulfment of stressed and dying cells by tolerogenic macrophages. Supporting the clinical relevance of the CALR exposure pathway, the spontaneous or therapy-driven translocation of CALR to the surface of malignant cells, as well as intracellular biomarkers thereof, have been associated with improved disease outcome in patients affected by a variety of neoplasms, with the notable exception of multiple myeloma (MM). Here, we describe an optimized protocol for the flow cytometry-assisted quantification of surface-exposed CALR and PS on CD38+ plasma cells from the bone marrow of patients with MM. With some variations, we expect this method to be straightforwardly adaptable to the detection of CALR and PS on the surface of cancer cells isolated from patients with neoplasms other than MM.

Spatial transcriptomics of fetal membrane-Decidual interface reveals unique contributions by cell types in term and preterm births.

During pregnancy, two fetomaternal interfaces, the placenta-decidua basalis and the fetal membrane-decidua parietals, allow for fetal growth and maturation and fetal-maternal crosstalk, and protect the fetus from infectious and inflammatory signaling that could lead to adverse pregnancy outcomes. While the placenta has been studied extensively, the fetal membranes have been understudied, even though they play critical roles in pregnancy maintenance and the initiation of term or preterm parturition. Fetal membrane dysfunction has been associated with spontaneous preterm birth (PTB, < 37 weeks gestation) and preterm prelabor rupture of the membranes (PPROM), which is a disease of the fetal membranes. However, it is unknown how the individual layers of the fetal membrane decidual interface (the amnion epithelium [AEC], the amnion mesenchyme [AMC], the chorion [CTC], and the decidua [DEC]) contribute to these pregnancy outcomes. In this study, we used a single-cell transcriptomics approach to unravel the transcriptomics network at spatial levels to discern the contributions of each layer of the fetal membranes and the adjoining maternal decidua during the following conditions: scheduled caesarian section (term not in labor [TNIL]; n = 4), vaginal term in labor (TIL; n = 3), preterm labor with and without rupture of membranes (PPROM; n = 3; and PTB; n = 3). The data included 18,815 genes from 13 patients (including TIL, PTB, PPROM, and TNIL) expressed across the four layers. After quality control, there were 11,921 genes and 44 samples. The data were processed by two pipelines: one by hierarchical clustering the combined cases and the other to evaluate heterogeneity within the cases. Our visual analytical approach revealed spatially recognized differentially expressed genes that aligned with four gene clusters. Cluster 1 genes were present predominantly in DECs and Cluster 3 centered around CTC genes in all labor phenotypes. Cluster 2 genes were predominantly found in AECs in PPROM and PTB, while Cluster 4 contained AMC and CTC genes identified in term labor cases. We identified the top 10 differentially expressed genes and their connected pathways (kinase activation, NF-κB, inflammation, cytoskeletal remodeling, and hormone regulation) per cluster in each tissue layer. An in-depth understanding of the involvement of each system and cell layer may help provide targeted and tailored interventions to reduce the risk of PTB.

Nanohoops in membranes: confined supramolecular spaces within phospholipid bilayer membranes.

Nanohoops, an exciting class of fluorophores with supramolecular binding abilities, have the potential to become innovative tools within biological imaging and sensing. Given the biological importance of cell membranes, incorporation of macrocyclic materials with the dual capability of fluorescence emission and supramolecular complexation would be particularly interesting. A series of different-sized nanohoops-ethylene glycol-decorated [n]cyclo-para-pyrenylenes (CPYs) (n = 4-8)-were synthesised via an alternate synthetic route which implements a stannylation-based precursor, producing purer material than the previous borylation approach, enabling the growth of single-crystals of the Pt-macrocycle. Reductive elimination of these single-crystals achieved significantly higher selectivity and yields towards smaller ring-sized nanohoops (n = 4-6). The supramolecular binding capabilities of these CPYs were then explored through host-guest studies with a series of polycyclic (aromatic)hydrocarbons, revealing the importance of molecular size, shape, and CH-π contacts for efficient binding. CPYs were incorporated within the hydrophobic layer of lipid bilayer membranes, as confirmed by microscopic imaging and emission spectroscopy, which also demonstrated the size-preferential incorporation of the five-fold nanohoop. Molecular dynamics simulations revealed the position and orientation within the membrane, as well as the unique non-covalent threading interaction between nanohoop and phospholipid.

Thermal control of photothermal implants inspired by polar bear skin for the treatment of infected bone defects.

Photothermal therapy (PTT) encounters challenges in addressing deep tissue infections, characterized by limited penetration or potential hyperthermal damage to surrounding tissues, initiating undesirable inflammatory cascades. Inspired by polar bear thermal regulation, we present a "bio-based endogenic thermal-adaptive booster" implant coating. This coating integrates a photothermal poly(tannic acid) (pTA) layer, mimicking the "polar bear dark skin", securely linked with anti-inflammatory dexamethasone (Dex), resembling the "secretion", and a red blood cell membrane (RBCM) layer, forming the insulating "transparent fur". The RBCM "fur" demonstrates unexpectedly superior local heat storage, amplifying the photothermal effect of the pTA "skin" by 1.30 times and boosting localized photothermal antibacterial efficiency by 1.30-fold (approximately 99%) compared to those without RBCM. Furthermore, RBCM sustains Dex release and offers additional protection against thermal inflammation, releasing Dex 1.90 times more under NIR irradiation than under non-photothermal conditions. In a rat infectious bone model, the photothermal-boosting implant coating provides a favorable biological interface and achieves a 99.97% photothermal antibacterial ratio, enhancing osseointegration without evident tissue harm, evidenced by a 2.47-fold increase in bone volume fraction and a 2.24-fold reduction in pro-inflammatory cytokines compared to those lacking a RBCM. Insights derived from cell membrane-based thermal-adaptive coatings herald a paradigm shift in efficient and safe PTT.

Multilayered Exudative Bacillary Layer Detachment in Active Choroidal Neovascularization: A New Optical Coherence Tomography Sign.

In this article, we present three cases diagnosed with active choroidal neovascularization (CNV): two cases diagnosed with neovascular age-related macular degeneration (nAMD), and one case with myopic CNV in an elderly eye that presented a characteristic and unique optical coherence tomography (OCT) sign consisting of well-defined, circular-shaped multiple concentric layers of alternating iso-hyperreflective material located between the external limiting membrane and outer photoreceptor layers, which seems to be a multilayered bacillary layer detachment (BALAD). Multilayered exudative BALAD in active CNV may be a new and characteristic OCT sign. [Ophthalmic Surg Lasers Imaging Retina 2024;55:92-94.].

Catalytic pre-coat on ceramic nanofiltration membranes for segregation and Fenton cleaning of high-resistance colloids in direct surface water treatment

Ceramic nanofiltration (NF) is a promising alternative for direct surface water treatment, but is hampered for full-scale applications by fouling and a lack of eco-friendly cleaning regimes. In this work, an innovative reactive pre-coat layer, consisting of an iron oxychloride catalyst, was constructed on top of commercial ceramic NF membranes, for segregating a large-sized colloid fraction in canal water and Fenton cleaning with a hydrogen peroxide (H2O2) solution. The large-sized colloids (3−30 μm) were identified as dominant substances fouling the TiO2 separation layer of the pristine membranes, leading to a fast increase in their filtration resistance, in contrast to the small-sized colloids (<0.04 μm) and natural organic matter (NOM). As a consequence, the catalyst pre-coat layer with a pore size of 0.1–0.5 μm was able to segregate the large-sized colloids from the TiO2 separation layer during direct filtration of the raw water. Moreover, filtration under an acceptable flux of around 23 L m−2 h−1 did not cause pore clogging in the catalyst pre-coat. In addition, Fenton oxidation initiated by the catalytic pre-coat efficiently restored the filtration resistance, whereas sole H2O2 flush of the pristine membrane was not effective. In the meantime, the TiO2 separation layer of the membrane exerted a high NOM rejection of approximately 90%, measured as dissolved organic carbon, while the catalyst pre-coat on the membrane remained active in Fenton cleaning, over five one-day cycles. The findings of this work may provide guidance on the structural and functional design of a catalytic pre-coat layer for a dual purpose of foulant segregation and oxidative removal, particularly in response to key fouling-causing substances, during membrane-based treatment of real water matrices.

ZIF-8 membranes on ZIF-8-PVDF/PVDF dual-layer polymeric hollow fiber supports for gas separation

ZIF-8 membranes have attracted extensive research attention due to their ease of synthesis, stable properties, and wide applicability. Compared to expensive inorganic supports, organic polymer supports are more flexible and inexpensive. However, addressing the issue of weak adhesion between the surface of the organic support and the ZIF-8 membrane layer poses a significant challenge. In this study, we present a strategy for preparation of ZIF-8 membrane by the fabrication of an asymmetric dual-layer polymeric hollow fiber support using polyvinylidene fluoride (PVDF) as the material. The outer layer of the support is composed of PVDF embedded with ZIF-8 seeds, while the inner layer consists of pure PVDF. This approach addresses the weak adhesion between the support and the ZIF-8 membrane layer formed through a one-step solvothermal crystallization process. The effects of ZIF-8 seed size, content, and crystallization conditions on the membrane structure and performance are investigated. Under the synergistic molecular sieving effects of ZIF-8 continuous membrane layer and ZIF-8 crystals within the outer layer of the support, larger gas molecules are difficult to penetrate the membrane layer, making the resulting membrane highly selective for the gas separation. Under the optimal fabrication conditions, the H2 permeability of the ZIF-8 membrane is determined to be 1.52 ± 0.1 × 10−7 mol·Pa−1·s−1·m−2, with a H2/N2 ideal separation selectivity of 69.5 ± 4. This method demonstrates simplicity and high reproducibility for preparation of ZIF-8 membranes on dual-layer hollow fibers, and it is expected to be extended to the growth and fabrication of other MOF membranes.

Effect of pH, NaCl concentration, and mAb concentration of feed solution on the filterability of Planova™ 20N and Planova™ BioEX.

Virus filtration is one of the most important steps in ensuring viral safety during the purification of monoclonal antibodies (mAbs) and other biotherapeutics derived from mammalian cell cultures. Regarding the various virus retentive filters, including Planova filters, a great deal of data has been reported on the virus retention capability and its mechanism. Along with the virus retention capability, filterability is a key performance indicator for designing a robust and high-throughput virus filtration step. In order to obtain higher filterability, optimization of the feed solution conditions, and filter selection is essential; however, limited data are available regarding the filtration characteristics of Planova filters. Furthermore, for Planova 20N and Planova BioEX, the virus retention characteristics were reported to differ due to their respective membrane materials and layer structures. Whether these filters differ in their filtration characteristics is an interesting question, but no comparative evaluations have been reported. In this study, the filterability of the two filters was investigated and compared using 15 feed mAb solutions of a single mAb selected by design of experiments with different combinations of pH, NaCl concentration, and mAb concentration. The filterability of Planova 20N was affected not only by the feed solution viscosity, but also by the mAb aggregate content of the feed mAb solution and mAb-membrane electrostatic interactions. In contrast, the filterability of Planova BioEX decreased under some buffer conditions. These findings and the established design spaces of these filters provide valuable insights into the process optimization of virus filtration.

Double-Strip Array-Based Metasurfaces with BICs for Terahertz Thin Membrane Detection.

A double-strip array-based metasurface that supports the sharp quasi-bound states in the continuum (quasi-BICs) is demonstrated in terahertz regions. By tuning the structural parameters of metal strips, the conversion of BICs and quasi-BICs is controllable. The simulated results exhibit an achieved maximum Q-factor for quasi-BICs that exceeds 500, corresponding to a bandwidth that is less than 1 GHz. The optical response of quasi-BICs is mainly affected by the properties of substrates. Resonant frequencies decrease linearly with increasing refractive index. The bandwidth of quasi-BICs decreases to 0.9 GHz when n is 2.2. The sharp quasi-BICs are also sensitive to changes in material absorption. Low-loss materials show higher Q-factors. Thus, the selection of a suitable substrate material will be beneficial in achieving resonance with a high Q value. The sensitivity of DSAs for molecules is assessed using a thin membrane layer. The DSAs show high sensitivity, which achieves a frequency shift of 70 GHz when the thickness of the membrane is 10 μm, corresponding to a sensitivity of 87.5 GHz/RIU. This metasurface with sharp quasi-BICs is expected to perform well in THz sensing.

Balancing proton and mass transfers in cathode catalyst layer of high-temperature proton exchange membrane fuel cell via gradient porous structure design

The porous structure within the cathode catalyst layers (CLs) plays a crucial role in facilitating phosphoric acid (PA) invasion and oxygen diffusion, which was essential for establishing the triple-phase boundaries (TPBs) in high-temperature proton exchange membrane fuel cells (HT-PEMFCs).In this work, a gradient porous structure is deliberately constructed within the cathode CL by carefully controlling the microstructures of the double CLs. The effects of pore diameter distribution in the cathode CL and PA content in the membrane electrode assembly (MEA) on the single cell performance of HT-PEMFC are systematically investigated. By incorporating an appropriate amount of PA in the MEA, along with the optimized gradient porous structure, the inner pores effectively stored acid and prevented its outward diffusion. Simultaneously, the pores in the outer CL provided additional pathways for oxygen transfer. Consequently, the optimized gradient porous structure enhanced the peak power density of H2/Air fuel cells to 0.510 W cm−2 at a Pt loading of 0.5 mgPt cm−2, a notable improvement compared to 0.396 W cm−2 of the traditional single CL. The mechanism analysis further reveals that the cathode CL with gradient porous structure can successfully balance proton transfer and mass transfer, hence reducing the polarizations in fuel cell.