  Recently, Liu et al. reported that Ti2CTx MXene have ultra-high hydrogen
storage capacity (8.8 wt.%) at room temperature. For the purpose to clearly
understand the hydrogen storage (H-storage), the composition of studied samples
should be clearly characterized and the H-storage structure need be explored.
To achieve 8.8 wt.% capacity, 3 layers of H2 molecules need be stored in the
interlayer space of MXene with the structure of Ti2CF2H14. The H2 layers with
graphene-like 2D structure are in solid/liquid state at room temperature, which
is significant in the explore new materials with surprising properties.
