The Adsorption Mechanism of Hydrogen on FeO Crystal Surfaces: A Density Functional Theory Study

The hydrogen-based direct reduction of iron ores is a disruptive routine used to mitigate the large amount of CO₂ emissions produced by the steel industry. The reduction of iron oxides by H₂ involves a variety of physicochemical phenomena from macroscopic to atomistic scales. Particularly at the atomistic scale, the underlying mechanisms of the interaction of hydrogen and iron oxides is not yet fully understood. In this study, density functional theory (DFT) was employed to investigate the adsorption behavior of hydrogen atoms and H₂ on different crystal FeO surfaces to gain a fundamental understanding of the associated interfacial adsorption mechanisms. It was found that H₂ molecules tend to be physically adsorbed on the top site of Fe atoms, while Fe atoms on the FeO surface act as active sites to catalyze H₂ dissociation. The dissociated H atoms were found to prefer to be chemically bonded with surface O atoms. These results provide a new insight into the catalytic effect of the studied FeO surfaces, by showing that both Fe (catalytic site) and O (binding site) atoms contribute to the interaction between H₂ and FeO surfaces.