The experimental setup in the work of Hu et al. does not allow to conclude if protons (H + ) or protiums (H atoms) enter the layered material: For protons, immediate neutralization is expected, as the proton's electron affinity of 13.6 eV is significantly higher than the work function of the host materials, even for wide band gap insulators such as h-BN. On the other hand, any two H atoms encountering each other are expected to recombine immediately due to the high formation energy of H 2 (4.52 eV in gas phase). The observed transport process of hydrogen through h-BN and MoS 2 requires, therefore, further investigation.