Can impure hydrogen produce sustainable metals?

Humboldt Foundation awards Kaitlyn Mullin for research on affordable green metallurgy

At a glance:

• Award: Alexander von Humboldt Foundation awards Dr Kaitlyn Mullin, postdoctoral researcher at the Max Planck Institute for Sustainable Materials, with a Humboldt Research Fellowship.
• Research topic: Hydrogen can drastically reduce carbon emissions from metal production, but producing highly pure hydrogen is still costly. Can hydrogen mixed with other gases be used for metal production without compromising material quality?
• Approach: Study how hydrogen gas mixtures interact with iron ores and whether impurities can even improve the properties of new alloys.
• Potential impact: More affordable low-carbon metal production while creating stronger and more sustainable engineering materials.

Hydrogen as a substitute for carbon, is considered one of the key ingredients for climate-friendly metal production. However, producing pure hydrogen remains expensive and energy-intensive, limiting its widespread industrial use. The Alexander von Humboldt Foundation awarded Dr Kaitlyn Mullin with a Humboldt Research Fellowship to continue her research at the Max Planck Institute for Sustainable Materials and investigate whether abundant hydrogen-gas mixes can be used to produce advanced metallic materials at lower cost and without quality losses.

Turning impurities into useful ingredients

The global production of metals accounts for around 10% of worldwide carbon dioxide emissions. Replacing carbon-based reducing agents with hydrogen is widely regarded as one of the most promising routes towards climate-neutral metallurgy as hydrogen produces water instead of carbon dioxide during the extraction of metals from ores.

In practice, however, using pure hydrogen on an industrial scale remains a major challenge as producing and purifying hydrogen requires significant amounts of energy and drives up costs. Rather than treating small amounts of gases such as methane or nitrogen as unwanted contaminants, Mullin aims to investigate whether these gas mixtures could become part of the solution.

“If we can use hydrogen-gas mixtures rather than pure hydrogen, it could significantly accelerate the transition towards sustainable metal production. Moreover, these gas mixtures, when incorporated in a controlled way, could be used to strengthen the metal while alloying”, says Mullin. The challenge is understanding how these elements behave during metal production and how they influence the structure of newly formed alloys. Mullin will combine experimental set-ups with advanced modelling and atomic scale characterization to understand how hydrogen gas mixtures interact with metal ores and how new microstructures develop during processing. Iron-based materials will serve as the primary model system because of their enormous industrial relevance and their central role in the decarbonisation of the steel sector. The insights gained could later be transferred to other metallic materials and manufacturing processes.

About the researcher and the fellowship

Kaitlyn Mullin did her PhD at the University of California Santa Barbara (USA) on the development of refractory alloy design principles for additive manufacturing, before joining MPI-SusMat in September 2025. She has won several awards like the US-National Science Foundation Graduate Research Fellowship that supported her PhD studies. And in 2026, a TMS-AIME Champion H. Mathewson Award that recognizes her publications on the engineering application of metals.  

The Humboldt Foundation fosters academic collaboration between exceptional international scientists and researchers in Germany. Its fellowships are awarded to individuals with outstanding qualifications and distinctive research profiles. The freedom for recipients to select any host institution in Germany makes this award a significant honour for both, the researcher and the hosting institute.