Atomistic mechanisms and dynamics of hydrogen-based reduction of iron ores

NON-TECHNICAL ABSTRACT

Steel is one of the most important industrial materials, with more than 2 billon tons produced annually. Its production, however, comes at a steep price for the environment. Steelmaking accounts for 7-11% of all human-made greenhouse gas emissions.

Facing escalating pressure from governments and investors to reduce emissions, the steel industry is experimenting with green steel projects that reduce greenhouse emissions by using hydrogen instead of traditional carbon-intensive manufacturing. However, fundamental understanding of the chemical processes that transform Iron oxide into Iron by use of hydrogen is required before green steel technology can advance.

This process is called hydrogen-based direct reduction. This project uses highly advanced techniques to understand hydrogen-based direct reduction by acquiring never before seen observations of the chemical reaction at the level of atoms along various points throughout time. This project combines these atomistically resolved experiments with computation in tightly integrated feedback loops, to achieve new real-time observations which vary both spatially and temporally.

As part of this research program, students at the graduate and undergraduate levels are learning and using new microscopy, spectroscopy, kinetic measurement and modeling techniques to work on materials issues that are at the forefront of current energy and environmental research. Results from this project are also being incorporated into undergraduate and graduate courses as well as high school outreach programs.

TECHNICAL ABSTRACT

Although oxide reduction plays a crucial role in many technologically important processes, a significant portion of current knowledge is based upon work at the mesoscale that is too coarse to reflect underlying microscopic details. This project addresses this knowledge gap by elucidating the atomistic mechanisms underlying the hierarchical interplay of oxide reduction pathways.

By employing a unique combination of in situ experiments and coordinated theoretical modeling, this project elucidates i) the elemental steps of H2 adsorption leading to the onset of oxide reduction; ii) microscopic mechanisms governing the propagation of oxide reduction and microstructure evolution via multi-interfacial transformations; and iii) atomistic processes leading to reversible oxidation-reduction cycles due to the countering action of H2 and gaseous product H2O. Clearly addressing these questions provide essential insights into reaction active sites, transient states, mass transport mechanisms, reaction activation energies and reaction pathways.

The study identifies critical structural and chemical parameters for controlling the efficiency, kinetics and metallic yield, which are leading to more efficient H2-based direct reduction methods, with potentially high impact on the urgently needed decarbonization of the steel industry. The sum of experimental and theoretical efforts also provide fundamental knowledge for construction of predictive and hierarchical multi-scale models of oxide reduction that naturally link different reaction stages, relate the atomistic processes with the macroscale behavior, and open the door to tailoring gas-solid reactions via controlling underlying atomic processes.

Such fundamental insights are shedding light on other fields such as corrosion, electrochemistry and catalysis, where the prototypes of basic processes also occur.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.