Traditionally derived from fossil fuels, hydrogen production contributes significant CO2 emissions. In contrast, electrolysis powered by renewable energy offers a cleaner alternative, emitting only oxygen. Achieving large-scale green hydrogen output is considered essential for phasing out fossil fuels and accelerating the global energy transition.
Standard electrolysis splits water into hydrogen and oxygen using a membrane-separated electrode pair. However, the method is costly, prone to hydrogen leakage, and poorly suited to intermittent energy sources like solar or wind. DWE resolves these limitations by eliminating membranes and using redox-active materials that temporally or spatially separate the gas generation steps.
The review highlights multiple DWE methodologies and introduces tangible scale-up strategies for the first time. Contributors include Prof. Avner Rothschild (Technion), Prof. Mark D. Symes (University of Glasgow), Prof. Jens Oluf Jensen (Technical University of Denmark), Dr. Tom Smolinka (Fraunhofer ISE), along with H2Pro's Rotem Arad and Gilad Yogev, postdoc Dr. Guilin Ruan, and Glasgow doctoral researcher Fiona Todman.
Prof. Symes and his team at Glasgow were the first to demonstrate DWE in 2013 using solution-phase redox mediators and have since advanced the technology through various liquid-phase systems. He now leads commercialization efforts at Clyde Hydrogen Systems.
At Technion, Prof. Rothschild and collaborators developed nickel-based redox electrode technology in 2015, laying the groundwork for founding H2Pro in 2019. The firm now leads the effort to commercialize membrane-free, cost-effective DWE systems compatible with intermittent renewable power. H2Pro is currently scaling this technology for deployment in the world's first full-scale DWE installation.
Experts Jensen and Smolinka contribute deep knowledge in PEM and AEM systems, comparing traditional electrolyzer configurations with disruptive DWE concepts. Arad and Yogev bring industry-focused perspectives on translating DWE innovations into deployable green hydrogen infrastructure.
The review emphasizes the vast gap between lab-scale and industrial needs. While experiments yield less than a gram of hydrogen daily, commercial facilities must produce roughly one ton per day-a scale-up factor of a million. Reaching this level would require about one million industrial electrolyzers, most of which cannot cope with fluctuating solar and wind power inputs.
DWE's advantage lies in its redox-based energy buffering, which allows it to absorb renewable energy surges much like a battery. This compatibility with variable energy sources positions DWE as a pivotal technology for producing low-cost green hydrogen.
Global hydrogen markets currently total $250 billion annually. Experts forecast that scalable green hydrogen could double this figure within a decade, reaching $550 billion.
"Green hydrogen is expected to account for 10% of the future energy market," said Prof. Rothschild. "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. 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," added Prof. Symes. "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. 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 paper provides a forward-looking perspective on how DWE could transform global hydrogen production and drive progress toward a sustainable energy economy.
Research Report:Technologies and prospects for decoupled and membraneless water electrolysis
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Technion-Israel Institute of Technology
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