Paving the way towards green hydrogen at scale
Decoupled water electrolysis paves the way for producing green hydrogen on an industrial scale – a breakthrough that would disrupt the global energy market and help combat climate change
Technion-Israel Institute of Technology
A recent review in Nature Reviews Clean Technology presents, for the first time, a pathway for scaling up decoupled water electrolysis (DWE) technologies to produce industrial-scale green hydrogen.
Hydrogen, a key chemical feedstock, is usually produced from fossil fuels, generating high CO₂ emissions. Water electrolysis powered by renewable energy emits oxygen rather than CO₂ and offers a clean alternative. Green hydrogen production on an industrial scale is one of the holy grails of the energy transition, as it would unlock the potential of replacing the world’s dependency on fossil fuels.
Conventional electrolysis uses two electrodes separated by a membrane to split water into hydrogen and oxygen. This approach is expensive, suffers from internal hydrogen leakage, and is incompatible with intermittent solar and wind power. DWE overcomes these issues by separating the hydrogen and oxygen production in time or space, eliminating the need for membranes. Rather, it uses redox materials that can absorb and release ions from which oxygen or hydrogen are produced.
The article reviews different DWE methods and, for the first time, presents feasible scale-up pathways. The authors include leading experts from all over the world: Prof. Avner Rothschild of the Technion Faculty of Materials Science and Engineering, Prof. Mark D. Symes of the University of Glasgow, Prof. Jens Oluf Jensen of the Technical University of Denmark, Dr. Tom Smolinka of the Fraunhofer Institute for Solar Energy Systems ISE, Rotem Arad and Gilad Yogev from the company H2Pro, Technion postdoctoral fellow Dr. Guilin Ruan, and University of Glasgow doctoral student Fiona Todman.
Prof. Mark Symes and his collaborators at the University of Glasgow pioneered the original embodiment of decoupled electrolysis in 2013, using solution-phase redox mediators. He has continued his work on decoupled electrolysis using a variety of liquid-based systems and is actively trying to commercialize this technology through the company Clyde Hydrogen Systems.
In 2015, Prof. Avner Rothschild pioneered a new technology together with Technion colleagues Prof. Gideon Grader, Dr. Hen Dotan, and Dr. Avigail Landman, using nickel-based redox electrodes. Their breakthrough led to the founding of H2Pro in 2019. The company stands at the forefront of commercializing DWE. H2Pro’s patented technology entails a streamlined, membrane-less system, cost-effective materials, and low capital costs. H2Pro is currently scaling up this technology and preparing to install the world’s first DWE system. The system is ideally suited to cope with intermittent renewable energy sources such as solar and wind.
Prof. Jens Oluf Jensen and Dr. Tom Smolinka are world-renowned experts on state-of-the-art electrolyzer technologies. Their work in proton exchange membranes (PEM), anion exchange membranes (AEM), electrode materials, and their application in cell stacks for large capacity PEM and AEM electrolyzers provided valuable insight into the challenges of scale-up and operation of commercial electrolyzers, and a sound base for comparison of disruptive decoupled and membrane-less electrolyzer concepts. Rotem Arad and Gilad Yogev provide insights into transforming these concepts into technologies for green hydrogen production at scale.
This review is the first to detail feasible scale-up strategies for DWE. While lab-scale DWE experiments produce less than a gram of hydrogen per day, industrial systems must generate about a ton daily – a million times more! Indeed, meeting current hydrogen demand would require around a million full-scale electrolyzers. Conventional industrial electrolyzers, on the other hand, require a stable grid supply and can only be used to a limited extent with highly dynamic power fluctuations such as those caused by solar and wind energy.
DWE’s unique advantage lies in its energy storage capability via redox materials, functioning like an electrolyzer with a built-in battery. This allows it to buffer energy fluctuations from renewable sources, making it highly compatible with solar and wind systems, thereby offering a critical pathway to low-cost, green renewable hydrogen production.
The potential impact of scaling up green hydrogen production is huge. The hydrogen market is currently worth about $250 billion annually. Once it becomes available on an industrial scale, the market for green hydrogen is expected to reach $550 billion within ten years.
“Green hydrogen is expected to account for 10% of the future energy market. Once it becomes possible to produce green hydrogen at large-scale and sell it at reasonable prices, hydrogen will replace a large part of the energy used in industry, heavy transportation, and other sectors,” Prof. Rothschild predicted. “Traditional electrolyzers should evolve to fit this market and, as noted by Darwin, it is not the strongest species that survives through evolution but, rather, the one that is best able to adapt and adjust to the changing environment in which it finds itself. I believe DWE would be it.”
“Decoupled electrolysis is only about 12 years old. More conventional technologies, such as alkaline and proton-exchange membrane cells, have had decades (if not centuries) for development. This gives some context to the rate of scaling of some of the new decoupled systems starting to emerge,” elaborated Prof. Symes. “On the current trajectory, I expect that the next decade will see decoupled electrolysis systems becoming serious competitors to more conventional electrolyzers, especially for the conversion of renewable energy to green hydrogen.”
The new ideas presented in the review article are compelling and shed light on the long-term prospects of scaling up DWE technologies for the benefit of all humanity.
Journal
Nature Reviews Clean Technology
Method of Research
Experimental study
Article Title
Technologies and prospects for decoupled and membraneless water electrolysis
Shepherding atoms on the surface towards a greener future – maximising the usage of precious metals
image:
Dr Emerson Kohlrausch demonstrating how atoms are guided and bonded to precise locations on a carbon surface
view moreCredit: University of Nottingham
Researchers have demonstrated that by using argon plasma, metal atoms can be dispersed and guided to desired positions. This new strategy ensures that not a single atom goes to waste and maximises the use of rare and precious metals.
In a study published in Advanced Science, researchers from the University of Nottingham, the University of Birmingham, Diamond Light Source, and the EPSRC SuperSTEM demonstrate how using fast argon ions to engineer defects on carbon surfaces allows metal atoms to bind and self-assemble into ultra-thin, single-layer metal clusters, forming unusual 2D metal islands of sub-nanometre size.
Industry uses metals for catalysis, but some of these metals are precious and rare, utilising metals with maximum efficiency is vital to ensure a sustainable future. Green technologies, such as hydrogen production, are advancing very fast, but they put pressure on the limited supply of critical elements and create environmental crises on the planet.
“Every atom counts,” says Dr Emerson Kohlrausch, lead experimentalist on the study from the University of Nottingham’s School of Chemistry. “Precious and rare metals are vital for clean energy and industrial catalysis, but their supply is limited. We’ve developed a scalable strategy to ensure not a single atom goes to waste.”
Unlike conventional approaches that require element-specific conditions or chemical dopants, the team’s method exploits atomic ‘vacancies’, tiny holes created by argon ion bombardment on a carbon surface, as universal binding sites. These defect sites act as atomic traps that strongly anchor metal atoms, preventing them from forming larger and less efficient 3D nanoparticles.
Remarkably, the method proved effective across 21 different elements, including notoriously difficult-to-control metals such as silver and gold. “This is a one-size-fits-all solution,” says Professor Andrei Khlobystov. “We can create mono-, bi-, or even tri-metallic atomic layers, with each atom precisely where we want it. That level of control is unprecedented.”
Dr Sadegh Ghaderzadeh, who led the theoretical modelling, highlights the elegance of the approach: “What makes this method so remarkable is its simplicity. Rather than relying on complicated chemical reactions, it utilises the physical movement of atoms from one place to another, significantly reducing the number of variables involved. Therefore, we can accurately recreate the formation of these materials in computer simulations, which will guide further development of the new method.”
The innovation lies not just in trapping atoms, but in doing so under pristine, solvent- and air-free conditions that prevent site passivation. “What makes this so powerful, yet so difficult, is that we create highly reactive sites on the surface and release metal atoms under tightly controlled conditions. At that stage, both the atoms and the surface are extremely unstable and reactive. Even a slight loss of control can lead to an incorrect metal configuration, but with the right conditions, atoms lock into place permanently. It’s like catching lightning in a bottle, just at the atomic scale,” Dr Kohlrausch explains.
Applications of these single-layer metal clusters (SLMCs) range from more efficient hydrogen production and ammonia synthesis to CO₂ conversion and energy storage. The researchers achieved record areal densities of up to 4.3 atoms per nm² and proved stability in air for over 16 months, as well as in catalytic environments.
“We’re making 2D metal catalyst on any surface a reality,” says Dr Jesum Alves Fernandes, the project leader. “Our vision is to design materials where every single atom is active and working, and nothing is wasted. This is how we make catalysis truly green.”
The research is funded by the EPSRC Programme Grant Metal Atoms on Surfaces and Interfaces (MASI) for a Sustainable Future. More information is available at www.masi.ac.uk.
The University of Nottingham has a strong track record in championing nanoscience and nanotechnologies. The Nanoscale & Microscale Research Centre (nmRC) provides a unique set of instrumentation and allied expertise, all under one roof, to support a number of cross-disciplinary research projects from functional materials to quantum technologies to healthcare.
Journal
Advanced Science
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
One-Size-Fits-All: A Universal Binding Site for Single-Layer Metal Cluster Self-Assembly
Article Publication Date
4-Jul-2025
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