Hydrogen has become one of the key components of energy transitionBut its biggest challenge lies not so much in producing it as in truly purifying it. In practice, it usually comes mixed with other gases such as methane or carbon dioxide, and separating it accurately involves costly, slow, and very energy-intensive processes.
In this context, a group of researchers from the Institute of Materials Science of Madrid (ICMM-CSIC) has taken an important step: they have designed a new membrane for hydrogen purification capable of multiplying efficiency almost tenfold compared to standard commercial membranes, while also reducing manufacturing time from several days to just a few hours.
A molecular filter that breaks the classic balance between speed and precision
The membranes function as a nanoscale sieveThey act as a selective barrier that allows certain molecules to pass through while blocking others. In the case of hydrogen, the classic technical challenge lies in maintaining a balance between two parameters that almost always conflict with each other: permeability (how much gas passes through the material per unit of time) and selectivity (its ability to discriminate between different gases).
Typically, when the step speed is increased, the separation capacity worsensand vice versa. However, the results from ICMM-CSIC, published in the Journal of Membrane Science, show that this new mixed-matrix membrane manages to improve both aspects simultaneously: it increases hydrogen permeability by more than 800% and raises selectivity by around 30% compared to commercial polysulfone membranes.
This performance leap means that hydrogen passes through the membrane much faster without sacrificing the purity of the resulting gas, something especially relevant for applications that demand high purity hydrogenas the fuel cells or certain petrochemical processes.
The key: a custom-designed, porous-filled polysulfone matrix
To achieve this improved performance, the research team started with a material well known in the industry: polysulfoneA very stable thermoplastic polymer widely used in filtration systems. Based on this, a porous component has been incorporated that acts as an "active filler" inside the membrane.
This filler is based on a rigid, truxene-type structure, capable of forming hyper-crosslinked polymers with a huge internal surface areaThe mechanics are relatively simple to explain: these pores function as a network of microscopic tunnels that offer preferential passage routes for hydrogen, whose molecule is much smaller than that of other gases such as methane or carbon dioxide.
By introducing this porous powder into the polysulfone matrix, the polymer chains are prevented from packing in an overly orderly fashion. This "controlled disorder" increases the so-called free volume fraction, that is, the amount of small voids available in the structure where gas molecules can move. In practice, this generates a internal channel network which facilitates the flow of hydrogen and slows down the passage of larger molecules.
According to lead researcher Eva Maya, the membrane must simultaneously resist hydrogen pressure and retain some elasticity to avoid cracking under real operating conditions. The ICMM-CSIC study shows that, with a load of around 30% of this porous fill, an optimal balance between extreme permeability and mechanical resistance is achieved.
Above that percentage, the material tends to become too brittle, losing flexibility and compromising its use in demanding industrial environments. This limit sets the benchmark for future developments and potential scaling up to geometries such as hollow fiber, commonly used in gas separation plants.
Mechanochemistry: manufacturing in three hours what previously took three days
Beyond the performance of the membrane itself, one of the most striking aspects of the project is the porous component manufacturing methodInstead of resorting to traditional solution chemistry—which usually involves large volumes of solvents and long reaction times—the team has used mechanochemical synthesis.
This technique involves introducing chemical precursors into a ball mill, where mechanical impact forces the reactions without the need for liquid media. The result is a porous material with clean pores, free of solvent residue, and a rigid structure that maintains its open porosity for the passage of gases.
Thanks to this approach, the synthesis of porous fillers goes from taking around three days with traditional methods to being completed in just three hours. That is to say, the The production window is drastically reduced., something key when thinking about industrial scaling and costs.
In addition to saving time, mechanochemistry significantly reduces the use of toxic solvents and, consequently, the generation of hazardous waste associated with the manufacture of advanced materials. From an environmental perspective, this means that the hydrogen purification technology itself relies on a much cleaner production process.
According to those responsible for the study, this approach makes the new membrane a particularly attractive proposition for industry: it allows not only purify hydrogen more efficientlybut also to produce the filtration material with lower energy consumption and a more favorable environmental profile.
Impact on industry and fit within the European hydrogen strategy
Hydrogen is already an essential raw material in sectors such as petrochemical industry, refining and ammonia productionwhere it is used on a large scale. In many of these processes, however, hydrogen from fossil fuels is still used, the conditioning of which requires energy-intensive purification stages.
A membrane capable of multiplying the efficiency of this purification process can change several critical points in the chain: reducing energy consumption in gas separation, increasing the degree of purity in fewer steps, and simplifying currently complex process schemes. All of this contributes to lowering the final cost of hydrogen, especially the so-called green hydrogen produced by electrolysis, which also needs further treatment before use.
This development also comes at a time when Europe is accelerating its hydrogen strategy as a tool to decarbonize activities that are difficult to electrify, such as heavy transport, certain branches of the chemical industry, or steelmaking. In this context, improving production is not enough: optimization is necessary. the entire value chain, including gas purification and conditioning.
The technology developed at ICMM-CSIC fits into this broader vision. By combining a more efficient membrane with a more sustainable synthesis process, it offers a solution that addresses both operating costs and the environmental footprint of the gas separation infrastructure itself.
The authors of the study point out that industrial scalability still requires additional steps, but emphasize that the approach shows high potential to transform the way hydrogen is purified in European industry, reducing technical barriers that have so far hindered a more widespread adoption of this energy vector.
A predominantly female team leading the development
Behind this advance is a group made up mostly of female scientists at ICMM-CSICAmong them, in addition to Eva M. Maya, are researchers such as Sara Izquierdo, Nayara Méndez-Gil, Berta Gómez-Lor or Mar López-González, along with other specialists involved in the more chemical and materials science aspects.
The collaborative work of this team has made it possible to address simultaneously aspects of molecular design, polymer processing and optimization of key parameters such as free volume fraction, mechanical stability and membrane response under pressurized hydrogen flow.
His research provides an integrated view in which the macroscopic behavior of the membrane —that is, how much gas passes through and how it does so— is understood from the internal architecture of the material, from the rigid nature of truxene to the way in which the polysulfone that contains it is organized.
This multidisciplinary approach, in which chemistry, materials physics and process engineering go hand in hand, is precisely the type of approach considered necessary to deploy hydrogen technologies with real options for large-scale implementation in Europe.
In a context of high demand for decarbonization solutions, the fact that Spanish research centers are contributing international benchmark innovations In fields as specific as membrane science, it reinforces Spain's role in the clean hydrogen technology race.
Everything suggests that, rather than big headlines about miracle technologies, much of the future of hydrogen as an energy carrier will depend on discreet advances like this: materials capable of reduce consumption, shorten processes and minimize waste in critical steps such as purification. If this new generation of membranes can be moved from the laboratory to industry, the invisible barrier that currently hinders the expansion of hydrogen could become much more manageable.
