Patterned electrodes reveal how bubble spacing affects hydrogen production efficiency

As part of a Special Invitation Collection celebrating the 15th anniversary of the Global Young Academy (GYA), a UT team led by David Fernandez Rivas has presented new insights into how bubbles behave during hydrogen production. By designing electrodes that guide the formation and merging of bubbles, the team has taken a significant step toward enhancing the efficiency of electrolysis for green hydrogen production.

The GYA was launched in 2010 with strong University of Twente involvement, as it was co-founded by UT professors Hans Hilgenkamp and Wilfred van der Wiel. Since then, it has grown into a leading platform for early-career researchers worldwide. To mark its 15th anniversary, the academy invited contributions from members and alumni to showcase how young scientists tackle complex, global problems.

“This special invitation feels like closing a circle,” says David Fernandez Rivas, now an alumnus of the GYA. “UT was there at the birth of the academy, and 15 years later, we can show how our research over the past 10 years in Twente continues that mission: combining curiosity with real-world impact.”

Tiny cavities, controlled bubbles

Hydrogen is often produced through electrolysis, where bubbles form on electrodes as water splits into hydrogen and oxygen. But uncontrolled bubbles can block surfaces, reducing efficiency. However, bubbles often appear at random locations on electrode surfaces, complicating efforts to better understand them.

To overcome this, the UT researchers with access to the Nanolab cleanroom from the MESA+ Institute created silicon electrodes patterned with tiny hydrophobic cavities. These are places where bubbles can consistently form, which lowers the randomness and therefore increases the controllability of electrochemical processes.

What makes this study stand out is that the team varied the distance between the cavities. This allowed them to see how bubbles grow, merge, and detach depending on how close their neighbors are.

They discovered that when the cavities are closer together, bubbles break off more often and in smaller sizes. This also helps reduce the buildup of gas around the bubbles. However, it also leads to more coverage on the electrode, which is a bit of a trade-off that needs to be balanced. The work is published in the journal Small.

“We showed that bubbles are not just a nuisance on electrodes, but can actually help drive gas away from the electrode if cleverly managed,” explains Dr. Akash Raman, who carried out the research as part of his Ph.D. “By adjusting the spacing of the cavities, we identified trade-offs between blocking the electrode and improving transport.”