Molecular study on the growth mechanism of CO2-H2 binary hydrate promoted by electric field

Abstract

The storage and transportation of hydrogen (H2) are widely recognized as the main challenge of hydrogen utilization technology. The hydrate-based method is one of the safe and environmentally friendly hydrogen storage methods. However, the harsh generation conditions and slow growth rate of H2 hydrate hinder its industrial application. Therefore, exploring methods to reduce the reaction conditions of H2 hydrate and improve growth efficiency is worth further research. This study investigated the effect of different intensities of electrostatic fields (0–0.9 V/nm) on the growth of CO2-H2 binary hydrates through molecular dynamics (MD) simulation. Representative parameters such as growth configuration, number of cages, dipole moment, four body angular order parameters, mean square displacement, occupancy rate, etc. were analyzed. The T, P conditions used for the simulation were 255 K, 80 MPa, and 400 ns in duration. The results suggest that a certain range of electric field strength can increase the growth rate of CO2-H2 binary hydrates and reduce the conditions required for hydrogen hydrate formation. The growth-promoting effect of the electric field is primarily manifested in the increased growth rate of binary hydrates. Detailed analysis reveals that electric field of a certain strength can to some extent promote the multiple occupancy of H2 within cage structures, thereby enhancing the hydrate's ability to capture H2. These molecular insights are beneficial for the application of electrostatic field in hydrate-based technologies to improving the storage efficiency of H2 hydrate and the reuse of CO2.