## 4 Conclusions  
This study thoroughly investigates the dissociative adsorption process of hydrogen atoms on iron surfaces and observes significant changes in charge density due to electron rearrangement. These changes facilitate the formation of new Fe-H chemical bonds and the breaking of existing H-H bonds. Specifically, the electron density around iron atoms decreases, while it increases near hydrogen atoms. This electron transfer and the resulting increase in electron interactions strengthen the bond between hydrogen and iron atoms.  
The dissociative adsorption process involves complex interactions between hydrogen and iron atoms, triggering electron rearrangement that affects the overall charge density distribution within the system. This electron rearrangement is primarily driven by orbital hybridization, particularly between hydrogen's 1s orbital and iron's 4s orbital, along with direct interatomic interactions.  
Furthermore, thermodynamic analysis reveals that under operational conditions of 25 \({}^{\circ}\)C and 12 MPa, the Gibbs free energy change for hydrogen dissociation is \(-\)1.53 eV, indicating that the process is spontaneous under pipeline conditions. As temperature and pressure increase, the hydrogen adsorption process is enhanced, primarily due to a decrease in Gibbs free energy and an increase in chemical potential. Specifically, as the temperature rises from 15 \({}^{\circ}\)C to 30 \({}^{\circ}\)C, \(\Delta\)G decreases, demonstrating the promoting effect of temperature on the spontaneity of the adsorption process. Therefore, precise control over temperature and pressure is critical in the design and operation of hydrogen-blended natural gas pipeline systems. This helps optimize hydrogen transport and distribution and plays a crucial role in maintaining the integrity of pipeline materials and energy efficiency management.  
These findings provide essential theoretical support for developing more efficient and safer hydrogen transportation technologies. The research indicates that understanding the interaction between hydrogen and pipeline steel surfaces can offer theoretical foundations for mitigating hydrogen embrittlement, thereby ensuring safe and efficient hydrogen transport in natural gas pipelines. The results provide important theoretical support for future optimization of hydrogen transportation technologies and improvements in pipeline safety strategies, offering scientific insights for the sustainable use of hydrogen energy.  
Conceptualization, W.H., Z.L. and P.Z.; Methodology, W.H. and Z.L.; Data curation, X.Y. and R.L.; Writing original draft, W.H. and X.Y.; Formal analysis, P.Z.; Writing--review and editing, R.L. and W.H.; All authors have read and agreed to the published version of the manuscript.  
Figure 12: Variation of Gibbs free energy \(\Delta\)G and chemical potential \(\mu\) with pressure.  
**Funding:** This research was funded by the National Natural Science Foundation of China, grant number 52004208 and Science and Technology Plan of Yulin City, Shaanxi Province (CXY-2019-139).  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The data used to support the findings of this study are included within the article.  
**Conflicts of Interest:** The authors declare no conflicts of interest.