Hydrogen adsorption behavior on AXenes Na₂N and K₂N: a first-principles study

Abstract

It is a consensus that the hydrogen economy has come to a standstill due to the lack of feasible hydrogen storage solutions, especially, the suitable hydrogen storage materials. In this work, the potential of a new kind of two-dimensional (2D) AXenes, Na2N and K22N, as hydrogen storage materials are evaluated by the first-principles calculations. In particular, we find that Na2N in T phase indicates a hydrogen storage capacity as high as 6.25 wt% with a desirable hydrogen adsorption energy of –0.167 eV per H2 molecule and a desorption temperature of 216 K, identifying T-phase Na2N to be a very promising reversible hydrogen storage material. In accordance to our results, H2–Na2N interaction causes H2 charge polarization, which is responsible for the moderate binding strength. In addition, Gibbs adsorption free energy reveals that the system will be more stable as more H2 molecules are loaded on the surface.

A new concept of atomically thin p–n junction based on Ca2N/Na2N donor–acceptor heterostructure: a first-principles study

“…In our calculations, their lattice constants are 3.70, 3.52 and 3.05 Å, respectively, which are consistent with the previous results. 46,47 Considering the lattice mismatch with respect to the Ca 2 N monolayer, the discussion will be focused on the T-phase Na 2 N.…”