Hydrogen storage in multilayer Ti3C2T MXene

In this work, we systematically investigated the hydrogen storage properties of multilayer Ti 3 C 2 T x MXene using density functional theory (DFT) coupled with the quantum-thermodynamic model to include the thermodynamic effect on hydrogen adsorption and storage behavior over a wide range of applied pressure and temperature. In addition to the surface-adsorbed hydrogen, we show that the interlayer spacing is a plausible storage route that could contribute to an additional hydrogen storage capacity. Due to hydrogen-bond bounded multilayer Ti 3 C 2 T x , the insertion, diffusion, and adsorption of hydrogen molecules into the interlayer spacing of the multilayer structure require sufficient external pressure to overcome the energy penalty to separate the multilayer structure. Using DFT calculations, we presented a novel model in attempt to unveil the mechanism of the nanopump effect, and providing new insights into its underlying process from a theoretical perspective. The calculated upper bound of theoretical gravimetric storage capacity using DFT calculation for multilayer Ti 3 C 2 T x is ∼3.8 wt% H 2 . While at 77 and 300 K with external pressure of 25 MPa, the predicted gravimetric capacity employing the DFT and quantum-thermodynamic model are found to be ∼2.1 and 0.67 wt% H 2, respectively, and experimentally, these H 2 -stored multilayer Ti 3 C 2 T x structures can be verified based on our simulated XRD analysis. Based on this work, we believe that our current simulation model can provide a reasonable and realistic prediction of hydrogen storage capacity and a systematic study of hydrogen storage mechanisms in other two-dimensional (2D) layered materials, besides multilayer Ti 3 C 2 T x . • The theoretical upper bound of the H 2 storage capacity of multilayer Ti 3 C 2 T x using the interlayer spacing is 3.8 wt. % H 2 . • At 77 and 300 K with 25 MPa, the theoretical gravimetric capacity of multilayer Ti 3 C 2 T x is 2.05 and 0.67 wt. % H 2 . • A model to understand the nanopump effect is proposed. • Simulated XRD spectra are provided for experimental justification of hydrogen storage in multilayer Ti 3 C 2 T x .