Nickel Oxides Double Reduction Speed

Researchers at the Max Planck Institute for Sustainable Materials show that nickel oxides can accelerate hydrogen-based steel production by a factor of two, reducing energy consumption and supporting more sustainable metallurgical processes.

Nickel Oxides Accelerate Hydrogen-Based Steel Production

Steel and metal production are among the largest contributors to global greenhouse gas emissions, accounting for approximately 10% of global CO₂ emissions. At the same time, modern technologies depend on tailored steels and metals used in mobility, energy, infrastructure, safety, and medical applications. Hydrogen-based metal production offers a promising CO₂-free alternative. It also enables the integration of reduction, alloying, and microstructure design into a single production step. However, one major challenge has limited broader adoption: the relatively slow reduction kinetics of metal ores at temperatures below 800°C.

Researchers at the Max Planck Institute for Sustainable Materials (MPI-SusMat) have now demonstrated a way to overcome this limitation. Their study shows that specific metal oxides can act as catalytic precursors and significantly accelerate hydrogen-based reduction processes while reducing energy demand. The findings were published in Nature Synthesis.

Nickel Oxides Show Strong Potential for Stainless and Maraging Steels

Conventional alloy production typically involves three separate steps:

1. Reducing ores to metals
2. Mixing molten elements to create an alloy
3. Applying thermomechanical treatments to achieve the desired properties

Each step requires substantial energy and relies heavily on carbon-based processes, resulting in significant CO₂ emissions.

Previous work by the MPI-SusMat team demonstrated that hydrogen-based reduction can combine these three steps into a single metallurgical process.

In the latest study, Dr.-Ing. Xinren Chen, postdoctoral researcher at MPI-SusMat and first author of the publication, together with colleagues, shows that this one-step approach can be further enhanced through the addition of nickel oxide during the hydrogen-based reduction of iron ores to iron-nickel alloys.

The nickel oxides are co-reduced and form nanoporous nickel as a transient phase. This nanoporous nickel serves as a highly active catalyst precursor that enhances the reduction of iron oxides.

How Nickel Oxides Double Reduction Kinetics

According to Chen, adding nickel oxides during the reduction of iron oxides makes the overall process twice as fast. Using atom probe tomography and transmission electron microscopy, the researchers observed that nickel oxides are rapidly reduced into porous metallic nickel. The resulting nickel binds with neighboring iron oxides and forms an interface. When hydrogen reaches this interface, nickel facilitates the splitting of hydrogen molecules into highly reactive hydrogen atoms. These hydrogen atoms migrate across adjacent iron oxide surfaces through a process known as hydrogen spillover, accelerating reduction reactions.

The researchers found that reduction can begin at temperatures as low as 300°C, significantly below the ignition point of hydrogen. The resulting nickel-containing alloy is an important master alloy used in industrial steels, including stainless steel grades 304 and 316, as well as high-strength and cryogenic steels for automotive, energy, and medical applications.