Recent Advances in Polybenzimidazole Membranes for Hydrogen Purification

Palladium Membrane Applications in Hydrogen Energy and Hydrogen-Related Processes

In recent years, increased attention has been paid to environmental issues and, in connection with this, to the development of hydrogen energy. In turn, this requires the large-scale production of ultra pure hydrogen. Currently, most hydrogen is obtained by converting natural gas and coal. In this regard, the issue of the deep purification of hydrogen for use in fuel cells is very relevant. The deep purification of hydrogen is also necessary for some other areas, including microelectronics. Only palladium membranes can provide the required degree of purification. In addition, the use of membrane catalysis is very relevant for the widely demanded processes of hydrogenation and dehydrogenation, for which reactors with palladium membranes are used. This process is also successfully used for the single-stage production of high-purity hydrogen. Polymeric palladium-containing membranes are also used to purify hydrogen and to remove various pollutants from water, including organochlorine products, nitrates, and a number of other substances.

Carbon Molecular Sieve Membranes Derived From Dual-Cross-linked Polybenzimidazole for Enhanced H2/CO2 Separation

The need for efficient CO2 separation during hydrogen production from fossil fuels drives the development of advanced, energy-efficient solutions. Membrane technology offers a promising approach for separating CO2 from H2, which, however, faces the challenge of low H2/CO2 selectivity. To address this challenge, a novel strategy to cross-link polybenzimidazole (PBI) using potassium persulfate (K2S2O8) is proposed, followed by pyrolysis to fabricate highly selective carbon molecular sieve (CMS) membranes. The cross-linked PBI-derived CMS membranes exhibit significantly enhanced permeability and H2/CO2 selectivity compared to neat PBI-CMS membranes. For instance, the CMS membrane prepared from PBI cross-linked for 24 h and pyrolyzed at 900 °C (denoted as KPBI24 CMS@900) demonstrates outstanding molecular sieving capability. This membrane achieves an H2 permeability of 55 Barrer with an H2/CO2 selectivity of 48 tested at 100 °C, significantly surpassing its non-cross-linked counterparts and the 2008 Robeson upper bound. The design principles of this study provide a robust technical foundation for persulfate-cross-linked PBI and offer an innovative approach for preparing high-performance CMS membranes.

Recent progress in biopolymer-based electrospun nanofibers and their potential biomedical applications: A review

Tissue engineering offers an alternative approach to developing biological substitutes that restore, maintain, or enhance tissue functionality by integrating principles from medicine, biology, and engineering. In this context, biopolymer-based electrospun nanofibers have emerged as attractive platforms due to their superior physicochemical properties, including excellent biocompatibility, non-toxicity, and desirable biodegradability, compared to synthetic polymers. Considerable efforts have been dedicated to developing suitable substitutes for various biomedical applications, with electrospinning receiving considerable attention as a versatile technique for fabricating nanofibrous platforms. While the applications of biopolymer-based electrospun nanofibers in the biomedical field have been previously reviewed, recent advancements in the electrospinning technique and its specific applications in areas such as bone regeneration, wound healing, drug delivery, and protein/peptide delivery remain underexplored from a material science perspective. This work systematically highlights the effects of biopolymers and critical parameters, including polymer molecular weight, viscosity, applied voltage, flow rate, and tip-to-collector distance, on the resulting nanofiber properties. The selection criteria for different biopolymers tailored to desired biomedical applications are also discussed. Additionally, the challenges and limitations associated with biopolymer-based electrospun nanofibers, alongside future perspectives for advancing their biomedical applications, are rationally analyzed.

Substantially Improving CO2 Permeability and CO2/CH4 Selectivity of Matrimid Using Functionalized-Ti3C2Tx

Mixed-matrix membranes (MMMs) with favorable interfacial interactions between dispersed and continuous phases offer a promising approach to overcome the traditional trade-off between permeability and selectivity in membrane-based gas separation. In this study, we developed free-standing MMMs by embedding pristine and surface-modified Ti3C2Tx MXenes into Matrimid 5218 polymer for efficient CO2/CH4 separation. Two-dimensional Ti3C2Tx with adjustable surface terminations provided control over these critical interfacial interactions. Characterization (Raman spectroscopy, XPS, DSC, FTIR) indicated the formation of hydrogen bonds between the termination groups on Ti3C2Tx and the carbonyl groups of Matrimid, promoting enhanced compatibility and dispersion of MXenes within the polymer matrix. The resulting MMMs with 5 wt % Ti3C2Tx showed a 67% increase in CO2 permeability and an 84% enhancement in CO2/CH4 selectivity compared to pristine Matrimid membranes. Surface modification of Ti3C2Tx using [3-(2-aminoethylamino)propyl]trimethoxysilane (AEAPTMS) further enhanced compatibility, leading to MMMs with 140% higher CO2 permeability and 130% greater CO2/CH4 selectivity. Molecular simulations suggested that AEAPTMS functionalization improved interfacial interactions with Matrimid chains, increasing the affinity of MXenes toward CO2 molecules. Additionally, the elongation of gas pathways, polymer chain disruption, and the presence of interlayer nanogalleries contributed positively to the enhanced separation performance. This work provides insights into tailoring nanomaterial-polymer interfaces to address the challenges of gas separation, paving the way for environmentally friendly CO2 separation technologies.

Cationic groups in polystyrene/O-PBI blends influence performance and hydrogen crossover in AEMWE

This study examines the effect of various quaternary ammonium groups on AEMWE performance and hydrogen crossover in blends of quaternized polystyrenes with O-PBI. Due to their higher hydroxide conductivity (69 mS cm-1 at 80 °C, 90% RH), trimethylammonium groups enable AEMWE to reach 1.0 A cm-2 at 2.0 V. The trimethylammonium groups exhibit low hydrogen crossover, ranging from 1.5% to 0.3%, across current densities of 50 to 1000 mA cm-2. Low hydrogen crossover is essential for AEMWE in terms of safety and efficiency.

Perspectives and State of the Art of Membrane Separation Technology as a Key Element in the Development of Hydrogen Economy

Due to the objectives established by the European Union and other countries, hydrogen production will be a key technology in the coming decades. There are several starting materials and procedures for its production. All methods have advantages and disadvantages, and the improvements in their performance and decreases in operational costs will be decisive in determining which of them is implemented. For all cases, including for the storage and transport of hydrogen, membranes determine the performance of the process, as well as the operational costs. The present contribution summarizes the most recent membrane technologies for the main methods of hydrogen production, including the challenges to overcome in each case.

Reverse fabrication method of thin-film composite membranes for hydrogen separation

A reverse method involves the pre-formation of an Matrimid (MI)-selective layer, followed by a porous polysulfone (PSF) support deposition. The membrane exhibited a high H2/CH4 selectivity and a moderate H2 permeance. This study introduces a facile method to produce membranes with inexpensive materials.

Municipal solid waste treatment for bioenergy and resource production: Potential technologies, techno-economic-environmental aspects and implications of membrane-based recovery

World estimated municipal solid waste generating at an alarming rate and its disposal is a severe concern of today's world. It is equivalent to 0.79 kg/d per person footprint and causing climate change; health hazards and other environmental issues which need attention on an urgent basis. Waste to energy (WTE) considers as an alternative renewable energy potential to recover energy from waste and reduce the global waste problems. WTE reduced the burden on fossil fuels for energy generation, waste volumes, environmental, and greenhouse gases emissions. This critical review aims to evaluate the source of solid waste generation and the possible routes of waste management such as biological landfill and thermal treatment (Incineration, pyrolysis, and gasification). Moreover, a comparative evaluation of different technologies was reviewed in terms of economic and environmental aspects along with their limitations and advantages. Critical literature revealed that gasification seemed to be the efficient route and environmentally sustainable. In addition, a framework for the gasification process, gasifier types, and selection of gasifiers for MSW was presented. The country-wise solutions recommendation was proposed for solid waste management with the least impact on the environment. Furthermore, key issues and potential perspectives that require urgent attention to facilitate global penetration are highlighted. Finally, practical implications of membrane and comparison membrane-based separation technology with other conventional technologies to recover bioenergy and resources were discussed. It is expected that this study will lead towards practical solution for future advancement in terms of economic and environmental concerns, and also provide economic feasibility and practical implications for global penetration.

Proton-Conducting Polymer-Coated Carbon Nanofiber Mats for Pt-Anodes of High-Temperature Polymer-Electrolyte Membrane Fuel Cell

High-temperature polymer-electrolyte membrane fuel cells (HT-PEM FC) are a very important type of fuel cell since they operate at 150-200 °C, allowing the use of hydrogen contaminated with CO. However, the need to improve stability and other properties of gas diffusion electrodes still hinders their distribution. Anodes based on a mat (self-supporting entire non-woven nanofiber material) of carbon nanofibers (CNF) were prepared by the electrospinning method from a polyacrylonitrile solution followed by thermal stabilization and pyrolysis of the mat. To improve their proton conductivity, Zr salt was introduced into the electrospinning solution. As a result, after subsequent deposition of Pt-nanoparticles, Zr-containing composite anodes were obtained. To improve the proton conductivity of the nanofiber surface of the composite anode and reach HT-PEMFC better performance, dilute solutions of Nafion^®, a polymer of intrinsic microporosity (PIM-1) and N-ethyl phosphonated polybenzimidazole (PBI-OPhT-P) were used to coat the CNF surface for the first time. These anodes were studied by electron microscopy and tested in membrane-electrode assembly for H₂/air HT-PEMFC. The use of CNF anodes coated with PBI-OPhT-P has been shown to improve the HT-PEMFC performance.