Adsorption and dissociation of high-pressure hydrogen on Fe (100) and Fe2O3 (001) surfaces: Combining DFT calculation and statistical thermodynamics

Hydrogen (H 2 ) pipeline systems are fundamentally the same as natural gas pipeline networks, but face a more serious safety challenge due to potential hydrogen embrittlement (HE) risk. At present, H 2 trans-portation and storage are intentionally operated under high-pressure (HP) conditions (i.e., 5-20 MPa for transportation, 35-100 MPa for storage), which make H 2 under supercritical state (i.e., supercritical H 2 , s-H 2 ). In this study, the thermodynamics of H 2 at a wide combination of temperatures (30 0-90 0 K) and pressures (0.1-100 MPa) has firstly been established based on a lattice-molecule model for predicting the adsorption and dissociation of gaseous and supercritical H 2 on the Fe-based steel surface. The configura-tions of H 2 adsorption and dissociation on Fe (100) and Fe2O3 (001) surfaces were investigated through the density functional theory (DFT) calculation, and the corresponding mechanism was elucidated using hybrid orbital theory. By applying the combination of DFT calculation and statistical thermodynamics, the dissociative adsorption of HP H 2 on Fe (100) and Fe2O3 (001) surfaces upon varying temperature and pressure was predicted and the results well aligned with previously published experimental studies. Compared to the gaseous H 2 , s-H 2 was likely to be more active on the iron (Fe) and its oxide (Fe2O3) surface in terms of dissociating into H atoms and could cause steels more susceptible to HE. The results also confirmed that the presence of the Fe2O3 scale could protect pipeline steels from environmental hydrogen permeation under the investigated HP conditions.(c) 2022 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study established the thermodynamics of hydrogen at various temperatures and pressures, investigated the adsorption and dissociation mechanisms of high-pressure hydrogen on iron and iron oxide surfaces, and found that supercritical hydrogen was more active in dissociating on the surfaces, making steels more susceptible to hydrogen embrittlement.