The Journal of Physical Chemistry Letters Letter
Table 3. (a) Relevant Energies for Analysis of the Stabilities of the Obtained HER Candidates in the 2H-Derived Structuresa
and (b) Similar Table for the 1T Candidatesb
(a)
2H-MX2 ΔH ΔHhull ΔHhull ΔHexpt. ref 40 ΔH2H/1T P(|ΔG| ≤ 0.5)
RuS2 −0.31 −0.70 0.39 −0.71 no −0.01 1.00
NiSe2 −0.21 −0.34 0.13 −0.38 no 0.17 1.00
OsS2 0.34 −0.60 0.94 NA no −0.01 1.00
TaO2 −2.58 −3.00 0.42 NA no −0.07 1.00
ReO2 −0.91 −1.42 0.51 −1.52 no 0.05 1.00
RhS2 −0.11 −0.48 0.37 NA no 0.07 1.00
PdS2 0.01 −0.31 0.32 −0.28 yes 0.17 1.00
NbS2 −1.21 −1.20 −0.01 NA yes −0.04 0.98
ScS2 −1.46 −1.46 0.00 NA no −0.06 0.96
TiS2 −1.23 −1.37 0.14 −1.41 yes 0.15 0.96
TaTe2 −0.32 −0.45 0.13 NA yes 0.00 0.89
CoS2 −0.33 −0.48 0.15 −0.51 no 0.01 0.86
IrS2 −0.11 −0.48 0.37 −0.46 no 0.22 0.84
RhSe2 −0.17 −0.45 0.28 NA no 0.07 0.81
TaS2 −1.24 −1.22 −0.02 −1.22 yes −0.02 0.78
ZrS2 −1.55 −1.73 0.18 −1.99 yes 0.19 0.77
ScO2 −2.74 −3.17* 0.43 NA no 0.05 0.49
VS2 −1.16 −1.14 −0.02 NA no −0.02 0.46
ScSe2 −1.30 −1.25* −0.05 NA no −0.01 0.43
CrO2 −1.99 −2.15 0.16 −2.01 no 0.03 0.37
PdSe2 −0.02 −0.33 0.31 NA yes 0.22 0.37
(b)
1T-MX2 ΔH ΔHhull ΔHhull ΔHexpt. ref 40 ΔH1T/2H P(|ΔG| ≤ 0.5)
ScSe2 −1.34 −1.25* −0.09 NA no 0.01 1.00
MoO2 −1.79 −1.95 0.16 −2.04 no 0.31 1.00
RhS2 −0.32 −0.48 0.16 NA no −0.07 1.00
IrS2 −0.30 −0.48 0.18 −0.46 no −0.22 0.99
PbSe2 0.04 −0.31* 0.35 NA no −0.22 0.99
PbS2 0.03 −0.32* 0.35 NA no −0.28 0.98
PdO2 −0.48 −0.41 −0.07 NA no NA 0.97
WO2 −1.61 −1.89 0.28 NA no 0.24 0.94
CoS2 −0.34 −0.48 0.14 −0.51 no −0.01 0.94
RuO2 −0.71 −0.94 0.23 −1.05 no −0.20 0.92
IrO2 −0.70 −0.94 0.24 −0.86 no NA 0.92
MnO2 −2.00 −1.98 −0.02 −1.80 no −0.43 0.87
NiO2 −1.01 −0.79* −0.22 NA no NA 0.83
CrS2 −0.77 −0.71 −0.06 NA yes 0.12 0.83
MoS2 −0.66 −0.93 0.27 −0.95 yes 0.28 0.74
OsO2 −0.23 −1.10 0.87 −1.02 no NA 0.65
VO2 −2.47 −2.63 0.16 −2.48 no −0.10 0.43
TiO2 −3.10 −3.29 0.19 −3.26 no −1.11 0.43
GeSe2 −0.27 −0.34 0.07 −0.39 no NA 0.38
PtO2 −0.61 −0.62 0.01 NA no NA 0.36
WS2 −0.59 −0.78 0.19 −0.90 yes 0.18 0.35
VTe2 −0.40 −0.45 0.05 NA yes 0.00 0.27
TaTe2 −0.32 −0.45 0.13 NA yes 0.00 0.24
FeSe2 −0.48 −0.56 0.08 NA no −0.05 0.23
NbS2 −1.18 −1.20 0.02 NA yes 0.04 0.22
FeTe2 −0.11 −0.20 0.09 −0.25 no −0.02 0.16
aΔH denotes the calculated standard heat of formation. ΔHhull denotes the heat of formation of the most stable compound (i.e., at the convex hull)
in the OQMD database.38 The symbol * in superscript corresponds to the situation, where no bulk structure with the compound composition lies on
the convex hull according to the database. In that case, ΔHhull is calculated as a linear combination of several structures. ΔHhull denotes the difference
between the two previous columns; that is, it shows how much the 2D compound lies above or below the convex hull. ΔHexpt. indicates the
experimental standard heats of formation as listed in the OQMD database. Lebègue al.40 have analyzed the possibilities for forming 2D compounds
based on the layered character of the bulk structures and their result is also listed in the Table. ΔH2H/1T is the difference between the energies in the
two (possibly distorted) 2H and 1T structures. Finally, P(|ΔG| ≤ 0.5) is the probability that the free energy of hydrogen adsorption lies within 0.5 eV
from zero, as described in Figure 6. All the energies are in eV/atom. bNA in the seventh column indicates that due to massive reconstructions the
compound is discarded from the 2H class. All energies are in eV/atom.
DOI: 10.1021/acs.jpclett.5b00353
J. Phys. Chem. Lett. 2015, 6, 1577−1585
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