Electrowinning for Room-Temperature Ironmaking: Mapping the Electrochemical Aqueous Iron Interface.

Area of Science:

• Materials Science
• Electrochemistry
• Computational Chemistry

Background:

• Room-temperature ironmaking via electrowinning is a promising sustainable technology.
• Poor faradaic efficiencies due to the hydrogen evolution reaction (HER) hinder its practical application.

Purpose of the Study:

• To elucidate the fundamental mechanisms governing iron electrodeposition and HER at the Fe(110) aqueous interface.
• To identify key factors influencing efficiency and guide electrolyte design for HER suppression.

Main Methods:

• First-principles thermodynamic analysis.
• Construction of a surface Pourbaix diagram for the Fe(110) interface.
• Theoretical overpotential calculations for iron deposition and HER at different surface sites.
• Modeling of hydrogen absorption mechanisms.

Main Results:

• The iron surface thermodynamically favors adsorbate coverage.
• Step sites are predicted to be preferential for iron growth and more reactive for HER than terrace sites.
• Hydrogen absorption into the iron surface is endothermic.
• HER limiting potentials are competitive with iron plating potentials at step sites.

Conclusions:

• Understanding the surface thermodynamics and kinetics is crucial for optimizing electrowinning processes.
• Step sites play a critical role in both iron deposition and the competing HER.
• Electrolyte engineering to suppress HER at step sites is essential for improving iron electrowinning efficiency.