Australian researchers have made a step forward in addressing perhaps the biggest single obstacle to the large-scale roll-out of the hoped-for hydrogen economy: hydrogen embrittlement. This is the process whereby hydrogen causes high-strength materials, not least steel, to become brittle and crack. This means that hydrogen cannot be effectively stored and transported under high pressures.
“The future of a large-scale hydrogen economy largely comes down to this issue,” highlighted University of Sydney researcher Dr Yi-Sheng Chen. “Hydrogen is notoriously insidious; as the smallest atom and molecule, it seeps into materials, then cracks and breaks them. To be able to effectively produce, transport, store and use hydrogen on a large-scale, this is not ideal.”
The research team, co-led by Chen and Professor Julie Cairney, found that the addition of molybdenum to steel, which had been reinforced with metal carbides, greatly increased its ability to trap hydrogen. (Carbides increase the durability and strength of the steels to which they have been added.) The amount of molybdenum added to the steel was equivalent to only 0.2% of the total steel.
The researchers were able to observe the effect of the addition of the molybdenum using cryogenic atom probe tomography. This was a form of advanced microscopy pioneered by the University of Sydney. Using this technique, the team saw that, after the addition of molybdenum to the steel, hydrogen atoms were trapped in the cores of the carbide sites. This was not observed in the case of the current benchmark alloy, titanium carbide steel.
“The addition of molybdenum helped boost the presence of carbon vacancies – a defect in carbides that can effectively capture hydrogen,” reported Chen.
“We hope this study will get us closer to revealing exactly why hydrogen embrittlement occurs in steel, paving the way for large-scale solutions to hydrogen transport and storage,” stated Cairney.
Australia hopes to be a leader in the upcoming Hydrogen Age, and to achieve that position by 2030. Hence the research being carried out at the University of Sydney, funded by the Australian Research Council, with support from the university’s own 2019 Postdoctoral Fellowship and the Tiawan-University of Sydney Scholarship.