Unveiling Hydrogen-Based Direct Reduction Mechanisms of Multicomponent Oxides via In Situ High-Energy X‑ray...

Area of Science:

• Materials Science
• Sustainable Chemistry
• Nanotechnology

Background:

• Multicomponent oxide co-reduction with hydrogen is a carbon-neutral strategy for alloy synthesis.
• Controlling alloy microstructure is crucial for applications in catalysis and energy technologies.

Purpose of the Study:

• To investigate the influence of precursor state on the reduction pathways and microstructural evolution of multicomponent oxides.
• To target the synthesis of an equiatomic Cobalt-Iron-Manganese-Nickel (CoFeMnNi) alloy.

Main Methods:

• Utilized in situ high-energy X-ray diffraction to monitor the reduction process.
• Compared two precursor variants: mechanically mixed powders and pre-sintered oxide mixtures.
• Analyzed post-reduction microstructures to understand morphology and phase formation.

Main Results:

• Mechanically mixed powders reduced through halite, spinel, and Mn₃O₄ intermediates, forming body-centered-cubic, face-centered-cubic, and MnO phases.
• Pre-sintered oxides directly transformed into metallic and MnO phases.
• Precursor state significantly impacted microstructure, yielding either coarse or nanoporous morphologies.

Conclusions:

• The initial precursor design critically dictates the reduction pathway and final alloy microstructure.
• Tailoring precursor strategies can enable single-step synthesis of nanoporous alloys.
• These alloys show promise for catalysis and energy storage applications.