University of New South Wales (UNSW) Sydney researchers have used precise 3D imaging to show how trapped bubbles affect the efficacy of electrolysers in the production of green hydrogen.
The research addresses a critical bottleneck in industrial-scale electrolysers, where hydrogen bubbles are generated in the electrolyser during the operation and accumulate on the porous electrode, blocking reaction sites and limiting mass transport at high current densities.
UNSW School of Civil and Environmental Engineering (SCEE) Professor Payman Mostaghimi said the researchers found that the shape and structure of the porous electrode are just as important as the electrochemistry.
“If the structure is designed properly, you can stop bubbles from clogging the system and make it much more efficient,” Mostaghimi said.
X-ray imaging simulations to look inside the porous structures provided researchers unique access to observe gas bubble behaviour over time, without taking the cell apart.
“When water is split, we found tiny hydrogen and oxygen bubbles get trapped inside the electrode, blocking the reaction sites and slowing the movement of water and ions, effectively starving the catalyst of fresh water,” Mostaghimi said.
“We looked at the architecture of these porous materials and found that a highly ordered, uniform pore structure resulted in minimal gas trapping.”
“This tells us that the pore structure is directly linked to gas trapping, which gives manufacturers a pathway to designing more efficient systems,” he said.
operando synchrotron imaging
It was also the first time operando synchrotron imaging, coupled with state-of-the-art pore-scale numerical methods, had been used to visualise hydrogen bubble formation, growth, and accumulation during electrolysis.
“Before this, scientists couldn’t really see what was happening inside the electrode the way we could using our advanced technologies,” co-investigator in the project, UNSW SCEE Professor Ryan Armstrong said.
UNSW School of Minerals and Energy Resources Engineering Dr Ying Da Wang, who led the flow simulation and analysis said the work shows that mass transport limitations are fundamentally linked to electrode architecture, not just catalytic activity.
A colleague from the UNSW School of Chemistry said by combining real-time imaging, advanced two-phase flow simulations, and performance measurements, it can now be understood how the accumulation of hydrogen bubbles influences performance during water electrolysis.
Green hydrogen transport and storage
The researchers are now focussing on a techno-economic assessment of coupling green hydrogen production with transport and large-scale storage in underground porous reservoirs.
“By looking at production, transport, and underground storage together, we can show policymakers and industry what is actually feasible, and at what cost,” Mostaghimi said.
The new method to boost the efficiency of green hydrogen production, is published in an Energy & Environmental Science paper with co-authored with research collaborators from French energy company TotalEnergies and Swiss technology university EPFL.
