Hydrogen storage performance of MXene Zr₂CO₂ material decorated with Li atoms: a DFT study

In this work, we explore the potential of the MXene material Zr₂CO₂ for hydrogen storage using density functional theory (DFT) with DFT-D2 dispersion corrections. The adsorption energy of hydrogen molecules was calculated to identify the most stable adsorption sites. Two orientations, namely vertical and horizontal, were considered. The results show that the adsorption energy does not fall within the required range (-0.17 to -0.6 eV) for effective storage. To enhance storage efficiency, lithium atom decoration was employed as a modification strategy. The most stable sites for Li atoms' attachment to the surface were identified. The results indicate that the hydrogen storage performance is Significantly enhanced. The 8Li@Zr₂CO₂ structure can hold onto 16 H₂ molecules, with the adsorption energy falling within the optimal range, i.e., -0.162 to -0.233 eV. The adsorption of 16 H₂ molecules on the 8Li@Zr₂CO₂ system has a gravimetric hydrogen storage capacity (C_wt %) of 1.52% and a desorption temperature (T_D) of 234.148 K. Additionally, the material demonstrates stability and potential for reversible hydrogen storage at room temperature. However, further improvements can be achieved through structural modification or alternative surface functionalization.