Researchers at the University of New South Wales (UNSW) have used 3D X-ray imaging and modelling to show how gas bubbles trapped inside porous electrodes can reduce the performance of water electrolysers used to produce green hydrogen.
The findings, published in Energy & Environmental Science, come from a collaboration between UNSW, TotalEnergies and EPFL. The team examined how hydrogen and oxygen bubbles generated during electrolysis accumulate within porous electrode structures, blocking reaction sites and limiting mass transport at high current densities.
“Green hydrogen production through water electrolysis is essential for decarbonising hard-to-abate sectors such as steelmaking and heavy-duty transport,” says Prof. Peyman Mostaghimi from UNSW’s School of Civil & Environmental Engineering.
According to the researchers, bubble build-up can “starve” catalysts by impeding the movement of water and ions through the electrode. Their work points to electrode architecture—particularly pore shape and uniformity—as a key factor influencing bubble trapping, alongside the electrochemistry.
The team combined synchrotron X-ray imaging with simulations to observe bubble behaviour inside porous structures over time without disassembling the electrolyser cell. “We looked at the architecture of these porous materials and found that a highly ordered, uniform pore structure resulted in minimal gas trapping,” Mostaghimi says.
Professor Ryan Armstrong, a co-investigator from UNSW’s School of Civil & Environmental Engineering, said the approach enabled observation inside electrodes in ways not previously possible. The study also included pore-scale numerical methods to visualise bubble formation, growth and accumulation during operation.
Dr Ying Da Wang from UNSW’s School of Minerals & Energy Resources Engineering said the results indicate mass transport limitations are “fundamentally linked to electrode architecture, not just catalytic activity”. Dr Quentin Meyer, working with Professor Chuan Zhao from UNSW School of Chemistry, said combining real-time imaging, two-phase flow simulations and performance measurements helped clarify how bubble accumulation influences electrolyser performance.
The researchers say they are now extending their work into techno-economic assessment of linking 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 says.
