Tiny bubbles could raise green hydrogen energy use by more than 50%, study shows

Researchers in the US have developed a three-dimensional (3D) computer model that could make green hydrogen production far more efficient, by revealing how bubbles waste energy during water electrolysis. The computational tool was created by scientists at New York’s Cornell University and their colleagues at City University of Hong Kong. It reveals how tiny bubbles, formed during water electrolysis, can disrupt hydrogen production, and increase electricity consumption. At the same time, the team identified a critical bubble size beyond which energy losses rise. Their simulations suggest that keeping bubbles below this threshold could limit the additional voltage required due to an individual bubble to within three percent. The 3D model also uses a computational method that reduces the effort needed to run simulations by approximately 1,000 times, without actually compromising numerical accuracy. The scientists hope the findings could make green hydrogen much cheaper to produce. Why bubble size matters Green hydrogen is a clean energy fuel made by splitting water (H2) into hydrogen and oxygen through water electrolysis powered entirely by renewable sources like solar or wind energy. It emits zero carbon dioxide (CO2) during production, which means it could provide a cleaner alternative to fossil fuels in industries including steelmaking and chemical manufacturing. However, the hydrogen and oxygen bubbles that form during the process pose a significant challenge. As electricity passes through an electrolyzer, these bubbles develop on the electrodes where chemical reactions take place. They can, therefore, block the active reaction sites, keep water from reaching the electrode surfaces, or interfere with the movement of the charged particles. This causes the electrolyzer to use more electricity to produce hydrogen. To address this problem, research teams have long experimented with changing electrode shapes, adjusting liquid flows, and modifying surface properties to help the bubbles detach easily. Yet, calculating the precise amount of energy lost due to individual bubbles has remained difficult. “Experimentally it’s really challenging to isolate the impact of bubbles on each individual scale,” Lenan Zhang, PhD, an assistant professor at Cornell University’s Sibley School of Mechanical and one of the study’s lead authors, pointed out. A revolutionary approach For the project, the team built a 3D mathematical model that simulates processes across eight orders of magnitude in length. As per Weihong Li, PhD, an associate professor of mechanical engineering at City University of Hong Kong, and second lead study author, it works like a digital twin of an electrolyzer. It can reproduce real electrode shapes, materials, and operating conditions, while revealing microscopic processes that are difficult to observe experimentally. With the model, the researchers were able to examine individual hydrogen bubbles on an electrode in an alkaline electrolyzer. They figured out that bubbles cause the greatest energy losses when they block active electrode surfaces. What’s more, they managed to identify a critical bubble radius. Once a bubble exceeds this size, the extra voltage needed for electrolysis rises exponentially. Under certain simulated conditions, this extra voltage could exceed 50 percent of the voltage required without bubbles. Moreover, the scientists confirmed that the critical size depends on electrode geometry and how easily liquid spreads across its surface. They believe they could improve the efficiency by creating electrodes that release bubbles before they become too large. The team now plans to expand the model to test how multiple bubbles grow, merge, and interact. They also aim to combine the technology with computational optimization and 3D printing to develop more efficient electrode designs. The study has been published in the journal EES Catalysis. Get the latest in engineering, tech, space & science - delivered daily to your inbox.Based in Skopje, North Macedonia. Her work has appeared in Daily Mail, Mirror, Daily Star, Yahoo, NationalWorld, Newsweek, Press Gazette and others. She covers stories on batteries, wind energy, sustainable shipping and new discoveries. When she's not chasing the next big science story, she's traveling, exploring new cultures, or enjoying good food with even better wine.