Catalysts like Nickel oxides accelerate hydrogen-based steel production and make it more energy efficient
At the heart of steel production: This simplified illustration shows how hydrogen (white) reduces iron oxide (iron-gray, oxygen-red) and suggests the role of nickel (yellow) as a catalyst.
© Xinren Chen / MPI for Sustainable Materials
To the point:
- Green steel: Conventional steel and metal production is responsible for 10 percent of global CO2 emissions. Hydrogen-based production offers a sustainable alternative, but is relatively slow and energy-intensive.
- Accelerated reaction: Nickel oxides act as catalytic precursors for the iron oxide reduction, making it twice as fast.
- Technical relevance: By enabling faster and more energy-efficient reduction, this approach brings hydrogen-based steel production closer to practical industrial deployment.
Steel and metal production are among the largest contributors to global greenhouse gas emissions, accounting for approximately 10 percent of global CO2 emissions. At the same time, modern technology fully relies on having tailored steels and metals for applications in fields such as mobility, energy, infrastructure, safety and medicine. Hydrogen-based metal production offers a promising and CO2-free alternative and goes even further by integrating reduction, that means the transformation of iron oxide into elementary iron, alloying and microstructure design into a single production step. However, hydrogen-based metal production still faces a number of challenges on its path to widespread adoption, one of which is the relatively slow reduction kinetics of metal ores at temperatures below 800 degree Celsius.
A research team of the Max Planck Institute for Sustainable Materials has now discovered that adding specific metal oxides as catalytic precursors can double the reduction kinetics of hydrogen-based metal production compared to uncatalyzed processes and make the process more energy efficient. The researchers have published their findings in the scientific journal Nature Synthesis.
A promising catalyst for stainless and maraging steels
Conventional alloy production is typically a three-step process: first, reducing ores to metals, then mixing liquified elements to create an alloy, and finally applying thermomechanical treatments to achieve the desired properties. Each of these steps is energy-intensive and relies on carbon as both an energy carrier and a reducing agent, resulting in significant CO2 emissions and a high energy consumption. The Max Planck Institute for Sustainable Materials team showed before, that a hydrogen-based reduction process allows to merge these three process steps into one single step.
Xinren Chen, postdoctoral researcher at the Max Planck Institute for Sustainable Materials and his colleagues now show that this one-step metallurgical process can be enhanced by adding nickel oxide during the hydrogen-based reduction of iron ores to iron-nickel alloys. The additional nickel oxides are co-reduced and form nanoporous nickel as a transient phase. This nanoporous nickel acts as catalyst for the reduction of iron oxides and enhances their reduction rate.
Nickel oxides serve as a catalyst precursor and accelerate the reduction kinetics by a factor of two, compared to an uncatalyzed hydrogen-based reduction. This is possible as nickel oxides bind with neighbouring iron oxides, creating an interface. Nickel breaks the incoming hydrogen molecules into highly reactive hydrogen atoms. These atoms then move across neighbouring iron oxide surfaces, a process known as hydrogen spillover, enabling accelerated reduction reactions.
© Image taken from Nature Synthesis. DOI: 10.1038/s44160-026-01086-5
"Adding nickel oxides to an ongoing reduction process of iron oxides, makes the overall reduction twice as fast and the onset temperature of the reaction dicreases by 100 degree Celsius", explains Chen. "The resulting nickel-containing alloy is an important master alloy widely used in industrial steels, including stainless steels grades 304 and 316, as well as high-strength and cryogenic steels used for automotive, energy and medical applications."
Do other metal oxides have the same catalytic effect?
Using nickel oxides, the researchers successfully accelerated hydrogen-based iron ore reduction. Nickel is both thermodynamically and metallurgically compatible with iron, making it particularly effective in this process. "While other transition metal oxides have not yet been systematically evaluated, elements with similar properties, such as cobalt, are expected to exhibit comparable catalytic behaviour, offering promising directions for future investigation", says Dierk Raabe, managing director of the Max Planck Institute for Sustainable Materials.
"Our study provides a new scientific strategy for accelerating hydrogen-based reduction and improving process efficiency, while industrial implementation will require further technological and economic developments", adds Xinren Chen. "The competitiveness of hydrogen-based steelmaking depends strongly on the availability and costs of green hydrogen."
At the Max Planck Institute for Sustainable Materials, sustainable metal and alloy production is being explored from multiple perspectives, combining experimental and theoretical approaches. In solid-state direct reduction, the kinetics are governed by a complex interplay of factors including temperature, the choice of reductant and metal system, and catalytic effects. A deeper understanding of these coupled mechanisms is essential for guiding the development of next-generation, more sustainable and cost-efficient reduction technologies.
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