El Green hydrogen has become one of the major players of the energy transition, because it allows us to store and use energy without emitting CO₂ at the point of use. However, the major obstacle remains how to produce it cheaply, efficiently, and truly sustainably, without depending on fossil fuels or scarce and expensive materials.
In recent years, Research centers and universities around the world are exploring new materials and production routesFrom solar-activated perovskite-based ceramics to intermetallic alloys subjected to elastic deformation, photoactive metal-organic frameworks (MOFs) for photocatalysis, precious metal-free catalysts, and innovative solutions in electrolyzers and fuel cells, all of this is painting a comprehensive picture of the future of green hydrogen production.
Why green hydrogen is key to decarbonization
The interest in green hydrogen is not accidental: Energy production is experiencing a period of accelerated change. Marked by the urgent need to reduce emissions and cut the use of fossil fuels, hydrogen, as an energy carrier, offers a way to store surplus renewable energy and release it when needed.
Unlike a primary energy source, Hydrogen acts as a “chemical storage” of energyIt is generated from electricity or heat and then consumed in fuel cells, industrial processes, or mobility applications. When its source is renewable (solar, wind, hydroelectric, biomass, etc.), we call it green hydrogen.
The problem is that Today, most of the hydrogen used in industry comes from fossil fuels. (natural gas reforming, coal, etc.), which results in approximately 900 million tons of CO₂ emissions annually worldwide, according to the International Energy Agency. Changing this reality requires technologies capable of producing renewable hydrogen on a large scale and at competitive costs.
Furthermore, Renewable energy sources have one major limitation: they are intermittent and variable.Wind and solar power produce energy when there is wind or sun, not when the system needs it. Green hydrogen allows us to "store" that surplus energy and use it later, either to generate electricity again, to obtain green chemicals (ammonia, fertilizers, synthetic fuels), or to power industrial processes and heavy transport.
Therefore, Europe and Spain have placed green hydrogen at the heart of their decarbonization plans in the medium and long term, but its massive deployment depends directly on advances in new materials and more efficient processes.
Water electrolysis and new materials for electrolyzers
The most widespread and promising way to obtain green hydrogen on a large scale is the water electrolysis powered by renewable electricityIn this process, an electrolyzer splits the water molecule (H₂O) into hydrogen (H₂) and oxygen (O₂) without direct CO₂ emissions.
In the electrolyzer, Water is introduced into a cell with two electrodes separated by a membraneBy applying electricity, hydrogen is generated at the cathode and oxygen at the anode. The hydrogen is collected, compressed, and stored or sent directly for consumption; the oxygen is usually released or used in other applications (e.g., medical or industrial).
There are several types of electrolyzers, each with Advantages, limitations, and specific material requirements:
- alkaline electrolyzerMature technology, relatively cheap, but with lower current density and some flexibility limitations.
- Solid oxide electrolyzer (SOEC)It works at high temperatures, with good efficiency, although still in less commercial phases.
- Anion exchange membrane electrolyzer (AEM): combines some of the advantages of alkaline and membrane systems, allowing the use of catalysts without noble metals.
- Polymer Electrolyte Membrane (PEM) Electrolyzer: very compact, capable of working with high currents and generating very pure hydrogen, ideal for integrating variable renewables.
PEM technology is especially interesting for “cushioning” the fluctuations of renewable energyHowever, it has a major drawback: its reliance on critical materials such as platinum and iridium in electrodes and other components, which drives up costs and complicates its global scaling. In practice, real-world cases such as the Electrolyzer that drives industrial green hydrogen in Navarre They show the technological and material requirements for integrating PEM with renewables.
CSIC teams, such as those led by María Retuerto and Sergio Rojas, are focused on replace these precious materials with more abundant and cheaper alternatives that maintain high catalytic activity and durability. The goal is not only to reduce the cost of the equipment, but also to lessen the environmental impact associated with the extraction of platinum, iridium, or ruthenium.
Meanwhile, the CSIC's Institute of Carboquímica, with researcher Maria Jesus Lazaro at the front, develops AEM low temperature electrolyzers with new electrodes based on non-noble metals. This technology attempts to combine the best of both worlds: the simplicity and low cost of liquid electrolysis and the high purity and efficiency of PEM systems.
According to these studies, Polymeric anion exchange membranes allow the use of catalysts without platinum, iridium, or ruthenium. and still achieve high efficiencies. This opens the door to more economically competitive green hydrogen production with less dependence on critical raw materials.
New families of platinum-free catalysts thanks to elastic deformation
Another key area of research focuses on Develop alternative catalysts to platinum for the hydrogen evolution reaction (HER) in electrolyzers. Platinum remains the standard due to its extraordinary activity and stability, but its cost and scarcity make it unfeasible to meet all future demand with it.
Researchers at IMDEA Materials have shown that, instead of inventing entirely new materials from scratch, It is possible to drastically improve the performance of already known intermetallic alloys applying controlled elastic deformations.
In a study published in ACS Catalysis, the following were analyzed: intermetallic thin films of three low-cost systems: Ag₃In (silver and indium), Ni₃Fe (nickel and iron) and Ni₃Sn (nickel and tin). When these films were subjected to small elastic deformations (on the order of 1%), a notable jump in their catalytic activity for HER was observed.
The researchers verified that Tensile deformations enhance activity in Ag₃InWhile Compressive strains have similar effects on Ni₃Fe, Ni₃Sn and even platinum itselfIn one particularly striking case, a sample of Ni₃Sn stretched by 1,26% achieved approximately 71% of the efficiency of platinum.
The study, authored by researchers such as Jorge Redondo, Jayachandran Subbian, Miguel Monclús, Valentín Vassilev Galindo, Jon Molina and Javier Llorca, constitutes one of the first clear experimental demonstrations of how the Elastic deformation, without introducing defects or cracks, can modulate catalytic properties of a material.
This approach offers a a completely new roadmap for designing warp-optimized catalystsThey are also using machine learning screening techniques to identify promising combinations of non-precious metals and intermetals. The goal is to accelerate the discovery of materials that can match or approach the performance of platinum, but with much more favorable availability and cost.
Ceramic perovskites and thermochemical cycles with solar heat
Beyond electrolysis, there is another very powerful line of research in Spain based on to produce green hydrogen from water using only heat from the sunwithout the need for electricity. The work of the Chemical and Environmental Engineering Group (GIQA) and the Institute for Research in Technologies for Sustainability (ITPS) at Rey Juan Carlos University stands out here.
This team has developed new ceramic materials capable of participating in thermochemical water splitting cyclesThe principle is relatively simple to explain, although technologically very demanding: first, the materials are heated to high temperatures, releasing oxygen from their structure, and then they react with water vapor, generating hydrogen and recovering that oxygen.
The materials used belong to the family of ceramic perovskitesCeramic compounds with high oxygen mobility in their crystalline lattice. This mobility allows the material to oxidize and reduce repeatedly, withstanding many cycles without critical degradation.
One of the most interesting contributions of the work, published in the journal CatalysisTodayIs that These new perovskites operate below 1000°CThis is in contrast to the 1300-1500°C required by other conventional thermochemical systems. This temperature reduction results in considerable energy savings and makes the use of solar reactors more viable.
The researcher María Linares SerranoGIQA highlights that The reduction-oxidation cycle can be repeated many timesThis makes the technology a promising option for the continuous production of renewable hydrogen in plants that directly harness concentrated solar radiation.
Furthermore, the team has not limited itself to trials with ceramic powders. They have molded the perovskites into macroscopic formats much closer to real-world use, such as:
- Ceramic pellets compact.
- Porous ceramic foams with a large specific surface area.
- Thin layers deposited on monolithic supports, very suitable for flow reactors.
These configurations improve the contact between the solid and the gases, as well as the heat transfer inside the solar reactorThe tests have shown significant increases in the amount of hydrogen produced, with the thin layers on ceramic monoliths being particularly outstanding, achieving the highest production values within the study.
This advanced design of materials and geometries brings the possibility closer to volumetric solar reactors capable of producing green hydrogen on a large scaleFor a country with high solar irradiation like Spain, this production route based on direct solar thermal energy has remarkable strategic potential.
Photocatalysis and MOFs: producing hydrogen from wastewater
Another innovative approach almost completely dispenses with external electricity and relies on Photocatalysis to break down water using sunlightWithin this framework lies the Hylios project, which seeks to transform the model of wastewater treatment plants.
Hylios' objective is design materials capable of capturing solar energy and applying it to the production of green hydrogen from contaminated waterThe idea is to use photocatalytic reactors that, when exposed to light, split water without needing to connect the system to the electrical grid, thus reducing both energy costs and the complexity of the infrastructure.
Photocatalysis offers several advantages: Use simpler and potentially cheaper equipmentIt can work with lower quality water (reducing competition with drinking water) and fits very well with circular water economy concepts.
A central aspect of the project is the development of new titanium-based metal-organic materials (MOFs)Experts at IMDEA Energy have created the MOF IEF-11 (IMDEA Energy Frameworks), which combines photoactive titanium units with squaric acid. This material has achieved very high photocatalytic efficiencies in the water photosplitting reaction, comparable to titanium oxide, which until now has been the reference photocatalyst.
Currently, work is underway on Modify and stabilize this MOF to improve its durability and expand the range of solar radiation it is capable of absorbing. The challenge is to overcome the current shortage of long-term stable photoactive materials and, at the same time, transform wastewater treatment plants into small-scale green hydrogen production facilities integrated into the wastewater treatment process.
Hylios develops through a multidisciplinary consortium led by LantaniaThe project, which involves Ansasol, ITECAM, the Institute of Chemical Energy (ITQ) of the Polytechnic University of Valencia, and IMDEA Energy, will run until at least October 2026 and aims to drastically reduce energy costs and the environmental impact of water treatment and hydrogen production.
Electrolysis with new, more active multimetallic compounds
Beyond elastically deformed intermetallic catalysts, others are also being discovered multimetallic compounds that far exceed the performance of their individual components for the production of hydrogen by electrolysis.
Researchers University of Twente They have developed a new electrode material that contains five different transition metalsAlthough each of these metals is only moderately active on its own, the combined compound exhibits catalytic activity one to two orders of magnitude higher.
In laboratory tests, the activity of this material It outperformed individual compounds by a factor of up to 680.This result surprised even the research team, led by Chris Baeumer. The explanation lies in a clear synergy effect: the different metals "help" each other at the electronic and structural level, generating a much more catalytically active and stable surface.
The compound is made up of elements abundant in the Earth's crust, making it a a potentially viable alternative to replace platinum and iridium in high-performance electrolyzers. Currently, the activity has been validated in a laboratory environment and its behavior still needs to be tested on an industrial scale.
As the researchers point out, The combination of five different metals is complex and requires optimizing synthesis routes and scaling processes. Even so, the material offers a very promising basis for adjusting compositions, textures, and operating conditions in order to outperform current commercial electrocatalysts in efficiency and cost.
Challenges of materials, water and new renewable sources of hydrogen
Alongside the development of new catalysts and advanced ceramics, other factors must be taken into account. major challenges related to materials and water resources so that green hydrogen is truly sustainable.
On one hand, Conventional electrolyzers rely on precious metals (platinum, iridium, ruthenium), whose extraction entails severe environmental impacts: soil degradation, water pollution and damage to ecosystems, in addition to the geographical concentration of its reserves.
To reduce this dependence, Low-cost alternative catalysts are being investigated based on carbon derivatives, magnetic materials, or synthetic compounds developed through green processes. The idea is to broaden the range of options and reduce both the economic and environmental costs of the supply chain.
Furthermore, the availability of quality water It's a sensitive issue. To produce one ton of green hydrogen through electrolysis, around nine tons of pure water are needed. In a context of increasing water scarcity, competition between water for human consumption, agriculture, and industry could become a serious bottleneck.
In response, avenues such as the use of seawater, urban and industrial wastewater, or even the use of ambient humidityTechnologies like H2umidity, developed by specialized companies, allow water to be generated from atmospheric humidity and used in electrolyzers, reducing pressure on conventional water sources. Furthermore, projects such as CIUDEN validates storage systems for integration with solar and green hydrogen, facilitating the viability of more complete renewable chains.
The production of green hydrogen from biomass and wasteThe Institute of Chemical Technology (ITQ), for example, is working on pilot plants that transform bioethanol from agricultural and wine industry waste into hydrogen by steam reforming at 500-700 °C and atmospheric pressure.
In these processes, the following occurs dihydrogen (H₂) which can be used to generate both electricity and heat in solid oxide fuel cells (SOFCs) as well as for synthesizing non-polluting fuels. Part of the hydrogen and heat generated is reinvested in the plant itself, improving its energy self-sufficiency and reducing external demand.
ITQ also investigates microwave-based technologies to transform electricity into hydrogen and other chemicals using ionic materials that release oxygen from their structure. This approach, patented and published in Nature EnergyIt may have future applications in energy storage, synthetic fuels, or even in ultra-fast battery recharging through an almost instantaneous reduction of the entire electrode volume.
Industrial applications, biofuels and the hydrogen economy
Hydrogen is already used massively in industry, especially for refining oil and producing ammonia and fertilizersbut it mostly comes from natural gas. Replacing this “gray” hydrogen with green hydrogen could substantially cut emissions from the industrial sector; Sidenor successfully tests green hydrogen at its Basauri steelworks, which illustrates real industrial applications in sectors with high energy demand.
ITQ teams project pilot plants that integrate green hydrogen into industrial processes so that the hydrogen itself supplies part of the plant's energy needs. In this way, highly efficient loops are created, where the heat and electricity generated help sustain the production process itself.
At the Institute of Catalysis and Petrochemistry (ICP), groups such as the one led by José Miguel Campos they study the production of advanced biofuels using renewable hydrogenThe process combines vegetable oil waste with a hydrogen stream in catalytic reactors at 300-400 °C and about 20 atmospheres of pressure.
First, a mixture of carbon oxides, linear hydrocarbons, and water is produced; then, a second stage allows transform those hydrocarbons into fractions similar to gasoline, kerosene, and diesel, with an energy efficiency that can reach 85%, well above the typical performance of conventional internal combustion engines.
All these developments reinforce the idea that Green hydrogen will be a pillar of the future low-carbon economyprovided that basic research, demonstration projects and support policies (infrastructure investments, tax incentives, clear regulatory frameworks) continue to be promoted.
The sum of these advances in new materials—from solarized ceramic perovskites, strain-optimized intermetallic alloys, and precious metal-free multimetal composites, to photoactive MOFs and alternative catalysts for electrolyzers—is shaping a scenario in which Producing green hydrogen continuously, efficiently and with less environmental impact is no longer a distant promise and it is gradually approaching becoming a large-scale technological and industrial reality.
