Surface Phase Stability of Fe₂O₃(001) in Hydrogen Reducing Environments: A DFT and XPS Analysis

This study combines density functional theory (DFT) and ab initio thermodynamics calculations with X-ray photoelectron spectroscopy (XPS) investigations to identify the reduction properties of the Fe₂O₃(001) surface with implications for corrosion resistance, hydrogen transport, and energy safety. Ab initio thermodynamics modeling predicts fully hydroxylated surface stability across a broad range of pressures (1 × 10^–23to 1 × 10⁵mbar) and temperatures below 700 K, consistent with previous experimental studies. Above 800 K, exposures to 1 × 10^–4mbar H₂, 1 × 10^–4mbar O₂, or 1 × 10^–4mbar H₂+ 1 × 10^–4mbar O₂each yield unique XPS signals indicating a loss of −OH coverage, aligning with DFT predictions. Insight into the mechanism of reduction as a function of H₂exposure is provided, as well as conditions that promote further reduction toward Fe₃O₄. Theoretical and experimental investigations indicate the ability to maintain the Fe₂O₃protective layer of iron oxides that have been exposed to H₂environments by including trace amounts of aqueous O₂.