  Based on first-principles calculations we performed a systematic study of the
energetic stability, structural characterization, and electronic properties of
the fully oxidized $A_{2}B$, electrenes, with the following combinations, (i)
$A$=Ca, Sr, and Ba for $B$=N; (ii) $A$=Sr and Ba for $B$=P; and Y$_{2}$C, and
Ba$_{2}$As. We have considered one side oxidation of single layer electrenes
$(O/A_{2}B)$, and two side oxidation of bilayer electrenes
$(O/(A_{2}B)_{2}/O)$. We show that the hexagonal lattice of the pristine host
is no longer the ground state structure in the oxidized systems. Our total
energy results reveal an exothermic structural transition from hexagonal to
tetragonal (h$\rightarrow$t) geometry, resulting in layered tetragonal
structures [$(AOAB)^{t}$, and $(AO(AB)_{2}AO)^{t}$]. Phonon spectra
calculations and molecular dynamic simulations show that the $O/A_{2}B$, and
$O/(A_{2}B)_{2}/O$ systems, with $A$=Ba, Ca, Sr, and $B$=N, become dynamically
and structurally stable upon such a h$\rightarrow$t transition. Further
structural characterizations were performed based on simulations of the near
edge X-ray absorption spectroscopy at the nitrogen K-edge. Finally, the
electronic structure calculations and transport calculations reveal the
formation of half-metallic bands spreading out through the $A$N layers, which
are shielded by oxide $A$O sheets. These findings indicate that $(AOAB)^{t}$,
and $(AO(AB)_{2}AO)^{t}$, (with $B$=N) are quite interesting platforms for
application in spintronics; since the half-metallic channels along the $A$N or
$(A\text{N})_2$ layers (core) are protected against the environment conditions
by the oxidized $A\text{O}$ sheets (cover shells).
