only allow for calculations on rather coarse k-point grids. An
accurate interpolation of the band structure from these points
is not possible, since both methods are non-selfconsistent.
Nevertheless, we can compare the band structures obtained
with GLLB-SC with the two last occupied and two first unoccupied
eigenvalues of some k-points (mainly high-symmetry
points). For ZrS2 (Figure 1), the band structure and the
bandgap calculated with GLLB-SC is very similar to the ones
obtained from HSE06 and GW levels. Different levels of GW
differ from each other only by a constant shift corresponding
to the difference in the bandgaps. The situation is different
for BaHfN2 (Figure 2). Whereas the valence bands are
almost identical, there are significant changes in the conduction
bands. Around the G-point, the order of the two lowest
conduction bands changes from GLLB-SC through HSE06 to
G0W0. For both the cases, an increase of the level of selfconsistency,
from G0W0 to GW, has only the effect of a constant
shift of the unoccupied bands equal to the bandgap difference.
These two examples shows two cases of excellent
matching and differences between the methods, respectively.
Literature Review of the Candidate Materials
In this section, we list the information found in the literature
for the candidate materials of Figure 4. In the manuscript,
the materials with a realistic possibility of success have been
described together with BaSnO3 and In2O3 that are the candidates
of the list already known to the water splitting community.
We describe now the remaining materials.
• AlAgO2: Sheets et al. have shown that AlAgO2 has an
optical bandgap of 3.6 eV.3 In an unrelated study published
at almost the same time, Ouyang et al. found a
bandgap of 2.95 eV.4 While there is a significant difference
in bandgaps, both are too large for optimal absorption
from the solar spectrum.
• BaCdO2: this was originally synthesized by von Schnering.
5 Very little is known about this material.
• Ba3In2O6: initially synthesized by Mader et al. 6, is
toxic and harmful7. Very little is known about this material.
• Ba4LiCuO4(CO3)2: originally synthesized by Tams et
al..8 Very little is known about this material.
• Ba4NaCuO4(CO3)2: this material was initially synthesized
by Vernooy et al. 9 Very little is known about this
material.
• Ba2NaOsO6: this is a Mott-insulator and a ferromagnetic
material,10 which was originally synthesized by
Very little is known normally means it has only been synthesized once.
Stitzer et al. 11 The material is black, thus indicating its
bandgap is probably below 1.7 eV, and it is toxic.7
• CdIn2O4: originally synthesized by Shannon et al. 12
This material is typically n-type and can be highly doped.
Can be found in either a spinel, inverted spinel, or an orthorhombic
structure. This material has been shown to
have a bandgap of 2.67−3.24 eV.13
• Cs2PtBr6: this material was produced only one time, thus
there is little information on it.14
• Li2PbO3: there are two forms of this material,15,16 neither
have been investigated thoroughly. It is toxic and
harmful.7
• LiRhO2: Scheer et al. synthesized a a-LiRhO2.17 Hobbie
et al. synthesized a black b-LiRhO2.18 Little information
is known on the photochemical properties of
either of these phases.
• NaBiO2: it was originally synthesized by Schwedes et
al. 19 Very little information is known on this material.
• Na2PdCl4: this material is reddish brown, but slightly
soluble in water.20
• Na3BiO4: it was originally synthesized by Schwedes et
al. 21 Little is known about this material.
• NaCoO2: Takahashi et al. showed that theoretically the
bandgap should be 1.3 eV. 22 NaCoO2 can be oxidized
by iodine (redox potential 0.54 V vs NHE), thus it is
highly unlikely that this material will be stable enough
to do water oxidation.23
• NaRhO2: originally synthesized by Hobbie et al. 24 It
can be oxidized by Na2S2O8, thus it is unlikely that it
will be stable during O2 evolution conditions.25
• KAg2AsO4: this material has only been synthesized by
Curda et al. 26 There is very little information on this
material.
• K2PdBr4: this material has a bandgap of around 2 eV, but
it is water soluble.27
• Sr2FeWO6: this material is black, with a bandgap of
0.1 eV.28
Calculated Bandgaps
In this section, we report the chemical formulas, the ids, and
the bandgaps of the calculated 2400 materials. The information
reported here are also available electronically in the Materials
Project database1 and in the Computational Materials
Repository.2
3