Membrane Catalyst Research Articles

MOF incorporated Polyethersulfone/Polylactic Acid ultrafiltration membranes for the catalytic removal of dyes via persulfate activation

This study synthesized novel nanocellulose/zeolitic Imidazolate Framework nanocomposite blended Polyethersulfone/Polylactic Acid (PES/PLA-CNF@ZIF-8) membranes through a modified phase inversion process. This is the first time that a nanocellulose-MOF composite catalytic nanomaterial has been synthesized and used as an additive in polymeric membranes. The morphology and chemical structure of the membranes and nanoparticles were characterised by scanning electron microscopy (SEM), atomic force microscopy (AFM) and Fourier transform infrared (FTIR) respectively. Membrane wettability and crystalline structure were characterised by contact angle, and X-ray diffraction (XRD) analysis respectively. CNF@ZIF-8 modified membranes showed improved contact angle which decreased from 76° in the pristine membranes to 40° in 2 wt% membranes, bulk porosity increased from 74.3.3 % to 81.06 % while the pure water flux increased from 208.30 Lm-2h−1 to 348.73 Lm-2h−1. Further, the modified membranes showed an increase in surface roughness reaching 84.14 nm in 2 wt% membranes. The synthesized membranes have been used as catalysts in the activation of persulfate to degrade Rhodamine B dye. The modified membranes displayed a high catalytic effect (>90 %) in activating persulfate to degrade RhB dye when compared to pristine membranes which showed a degradation efficiency of < 35 %. The study found that the optimum parameters for pH, membrane (catalyst) dosage, oxidant and initial dye concentration were 5, 0.3 g, 0.4 mM and 10 ppm respectively. Quenching experiments showed that •SO4- and •OH radicals were responsible for the dye degradation, with •SO4- radicals playing a major role in the oxidative degradation of the RhB dye. The synthesized membranes showed good stability when tested within five cycles, with the membranes showing degradation efficiency ranging from 92.1 % in the 1st cycle to 91.9 % in the 3rd cycle, before decreasing to 75.3 % in the 5th cycle. This study has therefore shown that the synthesized PES/PLA-CNF@ZIF-8 membranes have potential for use as catalysts in the degradation of cationic dyes in wastewater treatment through persulfate activation.

Unveiling the synergistic mechanism of Co-Cu catalysts for efficient oxygen evolution reactions

The development of highly active electrocatalysts for Oxygen Evolution Reactions (OER) is critical in the field of energy conversion and storage. Among potential candidates, diatomic catalysts have demonstrated the potential to outperform monoatomic counterparts, though comprehensive studies on their reaction mechanisms remain limited. In this study, a Co-Cu diatomic catalyst was computationally designed using density functional theory (DFT), and four reaction pathways involving multiple intermediates (*O, *OH, *OOH, *2OH, *O + *OH) were calculated. The results indicate that the Co-Cu diatomic catalyst exhibits superior catalytic performance on pathway II (H2O → *OH → *2OH → *OOH → O2) with an overpotential of 0.27 V, overcoming the limitations imposed by the active site of conventional anion exchange membrane (AEM) catalysts. The high catalytic activity is attributed to the synergistic interaction between the metal atoms, bypassing the high-energy barrier step typically observed in conventional pathways. In this mechanism, the Cu d-band center is close to the Fermi energy level, enhancing electron transfer, while Co provides a stable adsorption site and effectively regulates the adsorption and conversion of reaction intermediates. These findings offer new strategies for the rational synthesis of bimetallic catalysts.

The Influence of Membrane Thickness and Catalyst Loading on Performance of Proton Exchange Membrane Fuel Cells

This paper explores the influence of membrane thickness and catalyst loading on fuel cell performance of commercially relevant membrane electrode assemblies (MEAs). A systematic study was carried out with MEAs comprised of commercially available Pt/C electrocatalysts and reinforced PFSA membranes to better understand the practical limitations of incorporating low platinum loadings and ultra-thin membranes in commercially viable MEA designs. Three different MEA configurations were compared where membrane thickness was either 15 or 10 μm and cathode catalyst loading was either 0.4 or 0.1 mgPt cm−2. Extensive in situ electrochemical characterization was carried out to extract the relevant physical and electrochemical parameters of each MEA configuration. By changing only one variable at a time, i.e., either thickness or catalyst loading, it was possible to deconvolute the specific contributions of membrane thickness and catalyst loading on fuel cell performance. Interestingly, as membrane thickness was reduced below 15 μm, no significant changes in fuel cell performance were observed as membrane interfacial effects begin to dominate compared to bulk transport effects. Conversely, reducing catalyst layer loading from 0.4 to 0.1 mgPt cm−2 introduces significant polarization losses attributed to a combination of kinetic and mass transport effects.

Enhanced Zinc-air battery performance and local electrochemical evaluation of atomically dispersed Co and Ni in S, N-codoped carbon nanofibers via scanning electrochemical microscopy

This study reports the successful synthesis of a novel electrocatalyst for oxygen reduction reactions (ORR), comprising S,N dual-doped carbon nanofibers with atomically dispersed Co/Ni species (denoted as Co,Ni-SAs/S,N-CNFs), leveraging electrostatic spinning to achieve a unique spatial architecture that maximizes both active site density and mass transport efficiency. Density functional theory (DFT) analysis identified the initial proton-electron transfer to adsorbed O2 as the rate-limiting step, with CoN3S1-NiN3S1 emerging as the pivotal active site structure catalyzing this critical reaction. The fabricated Co,Ni-SAs/S,N-CNFs electrocatalyst exhibited remarkable ORR performance, characterized by a high half-wave potential of 0.84 V and a low Tafel slope of 57.9 mV dec-1. To gain a comprehensive understanding of its catalytic behavior, a tailored temperature-controlled scanning electrochemical microscopy (SECM) was employed, enabling the mapping of reactivity distribution under simulated operating conditions while preserving structural integrity. Liquid zinc-air batteries (ZABs) with this electrocatalyst excelled, reaching 175 mW/cm2 power density and enduring 1240 cycles. The electrospun membrane catalyst enabled both button and flexible ZABs, adaptable to diverse environments. This study advances non-precious metal electrocatalyst design and offers insights for ZAB applications, fostering green energy prospects.

Main-group element-boosted oxygen electrocatalysis of Cu-N-C sites for zinc-air battery with cycling over 5000 h

Developing highly active and durable air cathode catalysts is crucial yet challenging for rechargeable zinc-air batteries. Herein, a size-adjustable, flexible, and self-standing carbon membrane catalyst encapsulating adjacent Cu/Na dual-atom sites is prepared using a solution blow spinning technique combined with a pyrolysis strategy. The intrinsic activity of the Cu-N4 site is boosted by the neighboring Na-containing functional group, which enhances O2 adsorption and optimizes the rate-determining step of O2 activation (*O2 → *OOH) during the oxygen reduction reaction process. Meanwhile, the Cu-N4 sites are encapsulated within carbon nanofibers and anchored by the carbon matrix to form a C2-Cu-N4 configuration, thereby reinforcing the stability of the Cu centers. Moreover, the introduction of Na-containing functional groups on the carbon atoms significantly reduces the positive charge on their outer shell C atoms, rendering the carbon skeletons less susceptible to corrosion by oxygen species and further preventing the dissolution of Cu centers. Under these multi-type regulations, the zinc-air battery with Cu/Na-carbon membrane catalyst as the air cathode demonstrates long-term discharge/charge cycle stability of over 5000 h. This considerable stability improvement represents a critical step towards developing Cu-N4 active sites modified with the neighboring main-group metal-containing functional groups to overcome the durability barriers of zinc-air batteries for future practical applications.

Observing Electrochemical Performance Trends with the Physical Scaling of Bipolar Membrane Electrodialysis for the Capture and Concentration of Atmospheric CO2

Bipolar membrane electrodialysis (BPMED) is a proven technology for separating ionic species driven by electrochemical potential through ion conductive membrane separators. When using a bipolar membrane (BPM) as the separator, a pH gradient is created by the generation of acid and base via water dissociation at the internal interface of an anion conductive and a cation conductive membrane. BPMED can been used for the capture and concentration of atmospheric CO2, for example when using a liquid alkaline capture sorbent, where the acidification of the capture stream can be used to regenerate pure CO2 while further basification of the remaining effluent regenerates the alkaline capture sorbent to be re-used in the direct air capture process. Current commercial BPMs require high overpotentials to drive water dissociation and can only operate at low to moderate current densities. While considerable work has gone into the development of efficient, electrochemically active BPMs through improved membrane polymer chemistries and high-activity water dissociation catalysts, little work has been done to physically scale up these materials and use them in electrodialysis-driven carbon capture and concentration systems beyond lab scale (i.e., >1 cm2).In this presentation, we will report a scalable BPMED cell that can sense the resistive contributions of the individual membrane components (i.e., the anion exchange and cation exchange membranes, and the water dissociation at the internal BPM interface) with increasing membrane active area from 1 cm2 to 25 cm2. With this BPMED cell, changes in the BPM and water dissociation catalyst compositions and structures are related to electrochemical performance metrics (overpotential and CO2 recovery efficiency) at increasing physical scales. Electrochemical impedance spectroscopy (EIS) was used to reveal resistive contributions to the cell at increasing active area, while the inlet and outlet pH were measured to confirm the overall acidification and basification of the dialysis cell to promote carbon capture and conversion, as well as sorbent regeneration. This study aims to build a bridge between the necessary improvements in the membrane and water dissociation catalyst compositions with industrially relevant energy efficiency and conversion performance, accelerating the development of high performance BPMs.

The Impact of Catalyst Layer Fabrication Procedure on Layer Morphology, Transport Properties and Performance in Low-Temperature PEM Fuel Cell

Hydrogen mobility represents a progressive, low carbon imprint option for the replacement of internal combustion engines. A core of this technology is low-temperature fuel cell with proton-exchange membrane (LTPEMFC), using hydrogen and atmospheric oxygen as fuel and oxidant, respectively. The membrane-electrode assembly (MEA) which makes up a cell consists of polymer electrolyte membrane, cathodic and anodic catalyst layers and carbon-based porous gas-diffusion layers. LTPEMFC require Pt catalyst on both the anode and the cathode in non-negligible total amount, increasing investing costs for stack unit. In order to maximise fuel cell performance, the formation of three-phase boundary has to be achieved during deposition of catalyst layers, interconnecting Pt nanoparticles on carbon support and ionomer with membrane in complex, porous structure. The quality of catalyst layer determines to high degree final MEA performance.Catalyst layers can be deposited either on gas-diffusion layers or onto the membrane, with latter being considered a more advantageous and feasible approach. Deposition itself can be realised by various methods, including airbrush spraying, decal printing, doctor blade deposition from paste and, most often used nowadays, ultrasonically-assisted spray coating. Each of these methods brings its own advantages and disadvantages, though the common problem of these methods is low suitability for serial production. On the other hand, the quality of so-prepared catalyst layers is sufficient. Methods for large-capacity coating of catalyst layers, especially roll-to-roll technology have exactly opposite pros and cons, high output but unsatisfactory layer quality. An interesting alternative to state-of-the-art catalyst layer fabrication procedures is inkjet printing.Inkjet printing is a well-established technology, though the application in LTPEMFC field brings various issues, mainly connected to quality of layers and prevention of nozzle-clogging during the deposition. Solving of these issues, however, will result in technology suitable for catalyst layer printing, combining high production throughput, very good reproducibility, minimal losses of the ink, suitability to additive manufacturing and possibility of printing specific geometries with gradient layer thickness. Accordingly, the goal of this study is the comparison of catalyst layers, deposited onto the membrane by ultrasonically-assisted spray coating and inkjet printing, in terms of morphology, electric conductivity, permeability and performance in LTPEMFC, using commercially-available materials for layer fabrication.Catalyst layers of the same composition and Pt loading were deposited by either ultrasonically-assisted spray coating or inkjet printing onto FTO conductive glass for the determination of electric conductivity, onto gas-diffusion layer for permeability determination in Loschmidt cell and FIB-SEM morphology studies and onto the membrane for the fabrication of MEA and evaluation of its performance in LTPEMFC. Characterisation of layers deposited on materials above underlined feasibility of inkjet printing for catalyst layer fabrication. In comparison with sprayed layers, layers prepared by inkjet printing tend to be thinner, more homogenous and compact. This results in superior electric conductivity but lower permeability at the same time. Single cell tests proved that performance of inkjet-printed layers is at least on par with sprayed ones, surpassing them with optimised ink composition and Pt loading. Overall, inkjet printing technology is a highly attractive technology for industrial catalyst layer production with great possibilities for contributing to decrease LTPEMFC unit’s investment costs.This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 958174. This project is co-financed from the state budget by the Technology agency of the Czech Republic under the M-ERA.Net Programme, project No. TH80020006. This work was supported by the project "The Energy Conversion and Storage", funded as project No. CZ.02.01.01/00/22_008/0004617 by Programme Johannes Amos Commenius, call Excellent Research. This project is co-financed with tax funds on the basis of the budget passed by the Saxon state parliament.

Development of an Onboard Urea Electrolyser to Reduce NOx Emissions in Vehicles By Enhancing the Selective Catalytic Reduction with the Produced H2 and NH3

In the persistent pursuit of reducing nitrogen oxide emissions from diesel exhaust, challenges arise in achieving optimal performance at lower temperatures, especially in urban driving conditions. This research focuses on a pragmatic approach – development of an onboard urea electrolyser using diesel exhaust fluid (DEF) as the hydrogen-rich carrier. The primary goal is to enhance the NOx reduction efficiency at temperatures below 200oC by providing the electrolyser products – hydrogen and ammonia [1]. The reason behind this innovation lies in recognising DEF as a viable electrolyte, offering both safety and a promise of performance increase due to splitting of urea instead of water. Beyond the contribution to NOx reduction, this approach aligns with the broader societal and political imperatives of integrating cleaner energy solutions within the automotive sector. However, the development of a functional urea electrolyser involves certain complexities. The key considerations are the material stability under operating conditions, anode catalyst dissolution in DEF, mass transport limitations, and the reduction of relatively high cathode overpotentials. A notable aspect of our research involves addressing these challenges in scenarios both with and without potassium hydroxide alongside DEF, requiring a nuanced understanding of the electrochemical processes involved. Additionally, weight, packaging, and system integration play an important role in the development of an onboard urea electrolyser.This study systematically explores these challenges to devise a comprehensive understanding of the underlying electrochemical processes involved as well as the integration and operation strategy. The research methodology adopts single cell tests for which activation and measurement protocols have been established to achieve representative and comparable performance curve recordings and electrochemical impedance spectroscopy (EIS) data. Additionally, to various operating conditions of the electrolyte, the cell components screening adds to a considerable effort of this study. We explore the influence on the materials and design of the bipolar plates (BP) and porous transport layers (PTL); electrode performance and durability as well as the membrane selection. Within this study we consider anion exchange membranes (AEM) and bipolar membranes (BPM) for the performance comparison. Adopting both catalyst-coated membrane (CCM) and catalyst-coated substrate (CCS) approaches enables for examination of electrode preparation techniques and their influence on performance of the electrolysis cell. The initial results are promising, especially when employing 1 M KOH in the DEF electrolyte at 70oC, reaching 0.85 A cm-1 at 2 V. The respective performance curve is presented in Figure 1., together with a diagram of the electrolyser system integration into an existing Diesel exhaust line.This research represents a practical stride towards realising the denitrification of transportation sector especially in city cycle driving when the exhaust gases temperature is too low for the state-of-the-art SCR systems. By addressing identified challenges and optimising key parameters, our study lays a robust foundation for the scalable implementation of a functional urea electrolyser for transport applications and a basic understanding of the electrochemical processes behind the performance and stability of such a system.Figure 1.Depicts a recorded polarisation curve of a single cell using an anion exchange membrane (AEM) and nickel catalyst anode fed DEF and 1 M KOH as an electrolyte at 70oC. Below, the suggested integration of the electrolyser into latest generation Diesel exhaust aftertreatment system. It includes diesel oxidation catalyst (DOC), selective Diesel particulate filter (sDPF), hydrogen supported denitrification catalyst ‘H2-deNOx’ and finally a selective catalytic reduction (SCR) step.Reference: Esser, E., Kureti, S., Heckemüller, L., Todt, A. et al., "Low-Temperature NOx Reduction by H2 in Diesel Engine Exhaust," SAE Int. J. Adv. & Curr. Prac. in Mobility 4(5):1828-1845, 2022, https://doi.org/10.4271/2022-01-0538. Figure 1

0.68% of solar-to-hydrogen efficiency and high photostability of organic-inorganic membrane catalyst

Solar-driven flat-panel H2O-to-H2 conversion is an important technology for value-added solar fuel production. However, most frequently used particulate photocatalysts are hard to achieve stable photocatalysis in flat-panel reaction module due to the influence of mechanical shear force. Herein, a highly active CdS@SiO2-Pt composite with rapid CdS-to-Pt electron transfer and restrained photoexciton recombination was prepared to process into an organic-inorganic membrane by compounding with polyvinylidene fluoride (PVDF). This PVDF networked organic-inorganic membrane displays high photostability and excellent operability, achieving improved simulated sunlight-driven alkaline H2O-to-H2 conversion activity (213.48 mmol m−2 h−1) following a 0.68% of solar-to-hydrogen efficiency. No obvious variation in its appearance and micromorphology was observed even being recycled for 50-times, which considerably outperforms the existing membrane photocatalysts. Subsequently, a homemade panel H2O-to-H2 conversion system was fabricated to obtain a 0.05% of solar-to-hydrogen efficiency. In this study, we opens up a prospect for practical application of photocatalysis technology.

Machine learning-assisted performance prediction from the synthesis conditions of nanofiltration membranes

Optimizing membrane fabrication conditions, including monomer and catalyst concentrations, reaction time, etc., is crucial for achieving high-performance membranes. However, the multitude of variables involved can result in a complex and laborious permutation process, making trial-and-error optimization challenging. To address this issue, we developed a conventional multiple linear regression model and machine learning (ML) models, specifically random forest (RF) and multi-layer perceptron (MLP), to predict the performance of nanofiltration membranes in terms of key parameters such as pure water permeance or PWP (LMH/bar), Na2SO4 rejection (%), and NaCl rejection (%), based on specified input variable ranges. The input variables utilized to construct the models are the concentration of piperazine (PIP) (0.01–2 wt%), the concentration of trimesoyl chloride (TMC) (0.05–0.15 wt%), the concentration of sodium lauryl sulfate (SLS) (0–10 mM), and reaction time (5–1200 s). The conventional regression model failed to predict the membrane performance. The RF model exhibited the best prediction capability for PWP and NaCl rejection with the R2 of 0.9806 and 0.9812 for training, and 0.9669 and 0.9082 for testing, respectively. Similarly, the MLP model outperformed the RF model in predicting Na2SO4 rejection with an R2 of 0.9972 for testing and 0.9844 for training. The best membrane exhibited permeance ranging from 16 to 20 LMH/bar and selectivity between NaCl and Na2SO4 of over 4000, was facilitated by specific conditions. These conditions included lower concentrations of PIP (0.05–0.1 wt%), intermediate concentration of TMC (0.1 wt%), lower concentration of SLS (1 mM), and shorter reaction times (5–30 s). The best-performing ML-based models have been used to provide insights into the relative importance of these input variables in determining membrane performance, thereby aiding in correlating model predictions with fundamental principles of membrane fabrication processes.

Highly Efficient One-pot Electrosynthesis of Oxime Ethers from NOx over Ultrafine MgO Nanoparticles Derived from Mg-based Metal-Organic Frameworks.

Oxime ethers are attractive compounds in medicinal scaffolds due to the biological and pharmaceutical properties, however, the crucial and widespread step of industrial oxime formation using explosive hydroxylamine (NH2OH) is insecure and troublesome. Herein, we present a convenient method of oxime ether synthesis in a one-pot tandem electrochemical system using magnesium based metal-organic framework-derived magnesium oxide anchoring in self-supporting carbon nanofiber membrane catalyst (MgO-SCM), the in situ produced NH2OH from nitrogen oxides electrocatalytic reduction coupled with aldehyde to produce 4-cyanobenzaldoxime with a selectivity of 93 % and Faraday efficiency up to 65.1 %, which further reacted with benzyl bromide to directly give oxime ether precipitate with a purity of 97 % by convenient filtering separation. The high efficiency was attributed to the ultrafine MgO nanoparticles in MgO-SCM, effectively inhibiting hydrogen evolution reaction and accelerating the production of NH2OH, which rapidly attacked carbonyl of aldehydes to form oximes, but hardly crossed the hydrogenation barrier of forming amines, thus leading to a high yield of oxime ether when coupling benzyl bromide nucleophilic reaction. This work highlights the importance of kinetic control in complex electrosynthetic organonitrogen system and demonstrates a green and safe alternative method for synthesis of organic nitrogen drug molecules.

Highly Efficient One‐pot Electrosynthesis of Oxime Ethers from NOx over Ultrafine MgO Nanoparticles Derived from Mg‐based Metal‐Organic Frameworks

AbstractOxime ethers are attractive compounds in medicinal scaffolds due to the biological and pharmaceutical properties, however, the crucial and widespread step of industrial oxime formation using explosive hydroxylamine (NH2OH) is insecure and troublesome. Herein, we present a convenient method of oxime ether synthesis in a one‐pot tandem electrochemical system using magnesium based metal‐organic framework‐derived magnesium oxide anchoring in self‐supporting carbon nanofiber membrane catalyst (MgO‐SCM), the in situ produced NH2OH from nitrogen oxides electrocatalytic reduction coupled with aldehyde to produce 4‐cyanobenzaldoxime with a selectivity of 93 % and Faraday efficiency up to 65.1 %, which further reacted with benzyl bromide to directly give oxime ether precipitate with a purity of 97 % by convenient filtering separation. The high efficiency was attributed to the ultrafine MgO nanoparticles in MgO‐SCM, effectively inhibiting hydrogen evolution reaction and accelerating the production of NH2OH, which rapidly attacked carbonyl of aldehydes to form oximes, but hardly crossed the hydrogenation barrier of forming amines, thus leading to a high yield of oxime ether when coupling benzyl bromide nucleophilic reaction. This work highlights the importance of kinetic control in complex electrosynthetic organonitrogen system and demonstrates a green and safe alternative method for synthesis of organic nitrogen drug molecules.

Coordination-based synthesis of Fe single-atom anchored nitrogen-doped carbon nanofibrous membrane for CO2 electroreduction with nearly 100% CO selectivity

Carbon-based materials with single-atom (SA) transition metals coordinated with nitrogen (M-Nx) have attracted extensive attention due to their superior electrochemical CO2 reduction reaction (CO2RR) performance. However, the uncontrolled recombination of metal atoms during the typical high-temperature synthesis process in M-Nx causes deterioration of CO2RR activity. Herein, by using electrospinning, we propose a novel strategy for constructing a highly active and selective SA Fe-modified N-doped porous carbon fiber membrane catalyst (Fe-N-CF). This carbon membrane has an interconnected three-dimensional structure and a hierarchical porous structure, which can not only confine Fe to be single atom as active centers, but also provide a diffusion channel for CO2 molecules. Relying on its special structure and stable mechanical properties, Fe-N-CF is directly used for CO2RR, which presents an excellent selectivity (CO Faradaic efficiency of 97%) and stability. DFT calculations reveals that the synthesized Fe-N4-C can significantly reduce the energy barrier for intermediate COOH* formation and CO desorption. This work highlights the specific advantages of using electrospinning method to prepare the optimal SA catalysts.

Synergistically electronic interacted PVDF/CdS/TiO2 organic-inorganic photocatalytic membrane for multi-field driven panel wastewater purification

Solar-driven wastewater purification technology is a promising candidate to solve the hazards of water contaminants. However, it is difficult for most of particulate photocatalysts to maintain durable photoactivity due to its micro/nano size. Herein, a synergistically electronic interacted membrane catalyst with large extending area and high pollutant capture capacity was processed based on a highly active CdS/TiO2 heterojunction and ferroelectric polyvinylidene fluoride for achieving highly efficient Cr6+-to-Cr3+ (CTC) reduction (1.6×10−2 min−1) and synchronous decomposition of organic matters (methylene blue (1.2×10−2 min−1) and bisphenol A (0.6×10−2 min−1)) under simulated sunlight (SSL, 74.1 mW·cm−2) irradiation following a durably steady photoactivity even being recycled for 20 times, which effectively avoided the hazards of secondary pollution. Subsequently, a tailor-made panel wastewater purification system was first built based on this membrane catalyst to drive CTC reduction and synchronous organic matter degradation, and high-efficiency purification performance was presented on this panel system under multi-field drive of light-activation and piezoelectric polarization. This work provides an insight for photocatalytic wastewater purification through membrane catalyst assisted panel technology.

Mathematical Modelling and Simulations of Active Direct Methanol Fuel Cell

A one dimensional isothermal model is proposed by modelling the kinetics of methanol transport at anode flow channel (AFC), membrane and cathode catalyst layer of direct methanol fuel cell (DMFC). Analytical model is proposed to predict methanol cross-over rate through the electrolyte membrane and cell performance. The model presented in this paper considered methanol diffusion and electrochemical oxidation at the anode and cathode channels. The analytical solution of the proposed model was simulated in a MATLAB environment to obtain the polarization curve and leakage current. The effect of methanol concentration on cell voltage and leakage current is studied. The methanol cross-over has the significant impact on cell performance. The presented model predicts higher leakage current with the increase of methanol feed concentration. The cell performance was predicted at 70°C and various methanol feed concentration. The proposed model was validated with the experimental polarization curve of active DMFC.

Preparation of hierarchical TS-1 molecular sieve membrane catalyst and its catalytic performance for chloropropylene epoxidation

Preparation of hierarchical TS-1 molecular sieve membrane catalyst and its catalytic performance for chloropropylene epoxidation

Prospects of membrane catalysis in hydrogen energetics. Mini review

Hydrogen energetics is undoubtedly highly relevant today as it not only allows solving the issue of energy production from a renewable water source but can also prevent the formation of greenhouse gases. They say that any new idea is a well forgotten old one. The paper is dedicated to an excellent but still unimplemented work of Sainte-Claire Deville who managed to obtain hydrogen from water vapor using membrane technology. He used a clay pipe as a membrane which selectively permeated hydrogen. This process occurred with heating up to 950 °C. Sainte-Claire Deville managed to obtain only a mixture of hydrogen and oxygen in a ratio of 4:1 and then to clean the product from oxygen using chemical reactions. Modern membrane catalysts based on palladium or its alloys are selectively permeable only for hydrogen. This means that the membrane catalysis method with palladium membranes could allow to realize of hermal water disassociation more effectively and solve the issues of hydrogen energetics using only renewable raw materials. The history of hydrogen discovery and methods of its production was also studied in this review. Different methods of energy production were analyzed, including mineral resources, wind turbines, solar panels, hydroenergetics, electrolysis, and nuclear power, and a forecast was presented based on them. The review should be considered as an invitation to further discussions regarding this highly relevant and important topic

Tailoring graphitic nitrogen-enriched electrocatalytic membranes for acetaminophen degradation: Mechanistic insights into the site-specific reactive process

The pressing concern of pharmaceuticals and personal care products (PPCPs) in water, particularly with the increased usage of acetaminophen (ACE) during the COVID-19 pandemic, draws attention to the necessity for efficient water treatment. This study introduces tailored electrocatalytic carbon membranes featuring naturally doped nitrogen functionalities for energy-efficient electrochemical water treatment. The introduction of graphitic-N functionality into polyacrylonitrile electrospun fibers can be achieved through carbonization and activation processes, forming a freestanding electrocatalytic carbon membrane (ECM). In addition, in-situ immobilization of TiO2 on the ECM enables a deeper exploration of catalyst’s role in generating reactive oxygen species. As demonstrated, the enriched graphitic N in the membrane contributed to an enhanced electron transfer ability, resulting in extraordinary electrocatalytic activities. Note that graphitic N also served as site-specific active sites for ACE degradation. By utilizing the electrocatalytic carbon membranes, complete degradation of ACE was achieved within 60 min, with an electrical energy per order (EEO) of approximately 0.6 kWh/m3/order. This demonstrates the high degradation efficiency and low energy requirement of the system. Moreover, scavenger experiments demonstrate the significant involvement of O2•–, •OH and 1O2 in ACE degradation. Within the TiO2 decoration, there is a notable enhancement in the contribution of •OH during the degradation process. Overall, this study not only innovates electrocatalytic membrane design and catalyst immobilization but also advances our understanding of site-specific reactive processes in electrified water treatment.

Advanced development of anion-exchange membrane electrolyzers for hydrogen production: from anion-exchange membranes to membrane electrode assemblies.

Anion-exchange membrane water electrolysis (AEMWE) has attracted attention owing to its operation in alkaline environments, which offers the advantage of not requiring the use of precious metals. Additionally, AEMWE exhibits higher kinetics in the hydrogen evolution reaction, enabling higher hydrogen production efficiency. The anion-exchange membrane (AEM) fabrication, catalyst design, and membrane electrode assembly (MEA) are crucial for enhancing the total water electrolysis performance. There is an urgent need to summarize the advances in the development of AEMWE to pave the way for the commercialization of AEMWE. In this review, first, the fundamental principles of AEMWE technology are introduced. Second, the optimization of AEM with high ion conductivity and high stability through innovative synthetic methods are discussed in detail. Third, the designs of catalysts to increase the reaction rates by regulating the OH-adsorption environment and relieving OH blockage are introduced. Last but not least, a systematic summary of the concepts of 3D-ordered MEA, 3D-unified MEA, and 3D-self-supported MEA is presented. This review would be helpful to enhance the overall performance of AEMWE and promote the development of green hydrogen energy.

Effect of copper doping on the photocatalytic performance of Ni2O3@PC membrane composites in norfloxacin degradation.

In this study, copper (Cu) and nickel oxide (Ni2O3) microtubes (MTs) were synthesized using an electroless template deposition technique within porous polycarbonate (PC) track-etched membranes (TeMs) to obtain Cu@PC and Ni2O3@PC composite membranes, respectively. The pristine PC TeMs featured nanochannels with a pore density of 4 × 107 pores per cm2 and an average pore diameter of 400 ± 13 nm. The synthesis of a mixed composite, combining Cu and Ni2O3 within the PC matrix, was achieved through a two-step deposition process using a Ni2O3@PC template. An analysis of the resultant composite structure (Cu/Ni2O3@PC) confirmed the existence of CuNi (97.3%) and CuO (2.7%) crystalline phases. The synthesized catalysts were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) analysis, and atomic force microscopy (AFM). In photodegradation assessments, the Cu/Ni2O3@PC mixed composite demonstrated higher photocatalytic activity, achieving a substantial 59% degradation of norfloxacin (NOR) under UV light irradiation. This performance surpassed that of both Ni2O3@PC and Cu@PC composites. The optimal pH for maximum NOR removal from the aqueous solution was determined to be pH 5, with a reaction time of 180 min. The degradation of NOR in the presence of these composites adhered to the Langmuir-Hinshelwood mechanism and a pseudo-first order kinetic model. The reusability of the catalysts was also investigated for 10 consecutive runs, without any activation or regeneration treatments. The Cu@PC membrane catalyst demonstrated a marked decline in degradation efficiency after the 2nd test cycle, ultimately catalyzing only 10% of NOR after the 10th cycle. In contrast, the Ni2O3@PC based catalyst demonstrated a more stable NOR degradation efficiency throughout all 10 runs, with 27% NOR removal observed during the final test. Remarkably, the catalytic performance of the Cu/Ni2O3@PC mixed composite remained highly active even after being recycled 4 times. The degradation efficiency exhibited a gradual reduction, with a 17% decrease after the 6th run and a cumulative 35% removal of NOR achieved by the 10th cycle. Overall, the findings indicate that Cu/Ni2O3@PC mixed composite membranes may represent an advancement in the quest to mitigate the adverse effects of antibiotic pollution in aquatic environments and hold significant promise for sustainable water treatment practices.