1
Electronic Supplementary Information
Experimental Demonstrations of Spontaneous, Solar-Driven
P
hotoelectrochemical Water Splitting
Joel W. Ager,*
a
b
Matthew Shaner,
c
d
Karl A. Walczak,
a
b
Ian D. Sharp,
a
e
and Shane Ardo
f
a
Joint
Center
for
Artificial
Photosynthesis,
Lawrence
Berkeley
National
Laboratory,
Berkeley,
CA,
USA
E-mail:
JWAger@lbl.gov
b
Materials
Sciences
Division,
Lawrence
Berkeley
National
Laboratory,
Berkeley
CA,
USA
c
Joint
Center
for
Artificial
Photosynthesis,
California
Institute
of
Technology,
Pasadena,
CA,
USA
d
Division
of
Chemistry
and
Chemical
Engineering,
California
Institute
of
Technology,
Pasadena,
CA,
USA
e
Physical
Biosciences
Division,
Lawrence
Berkeley
National
Laboratory,
Berkeley
CA,
USA
f
Department
of
Chemistry,
and
Department
of
Chemical
Engineering
and
Materials
Science,
University
of
California
Irvine,
Irvine,
CA,
USA
The solar-to-hydrogen (STH) conversion efficiency and operation stability
of 47 reports
of spontaneous, solar-driven water
splitting are compiled in
Tables
2 – 5 of the
main
text.
Additional analysis on the
electrolyte conditions employed and the reported STH conversion
efficiency and device longevity are reported here.
Figure S1 shows a pie chart of these 47 reports binned by the pH of the electrolyte into
three pH
ranges:
acidic, 0-4; near-neutral; 4-10; and basic,
10-14. There are an approximately
equal number of acidic and basic
demonstrations;
about
a quarter of the demonstrations
used
near-neutral pH conditions.
Figure S1
. Pie chart showing the relative proportion of devices operating within a specified pH regime.
Electronic
Supplementary
Material
(ESI)
for
Energy
&
Environmental
Science.
This
journal
is
©
The
Royal
Society
of
Chemistry
2015
2
Figure S2 provides further analysis of the data shown in Figure S1 by separating
each pH
range by
type of system, including the number
of junctions:
2J, SLJ
, 2 junction tandem PV with at least
one semiconductor
–liquid junction
(SLJ), cf. Table 2;
2J, isolated PV, 2J tandem PV with all PV junctions
“buried”
including PV +
electrolyzer approaches, cf.
Table 3
3J, SLJ
, 3 junction tandem PV with at least
one semiconductor
–liquid junction
(SLJ), cf. Table 4;
and 3J,
isolated PV, 3J tandem PV
with all
PV
junctions “buried” including PV +
electrolyzer approaches, cf.
Table 5.
Nearly every
device category
has
a demonstration in one of the previously
defined
pH
ranges.
Figure S2
. Histogram
of the number of reports for each electrolyte pH
range, organized
by device configuration.
3
Figure S3 graphs the
STH
conversion efficiency versus
pH of the electrolyte, employing
the same
device
configurations as in Figure S2. This illustrates that
even
the largest
reported
STH conversion efficiencies
(i.e.
those close to or exceeding 10%) were operated over
a wide
range of pH values,
from
0 to 14. The
only device configuration that does not have
a reported
STH efficiency greater than 10%
is the
3J, SLJ
category.
Fig. S3
.
Reported
solar-to-hydrogen (STH) conversion efficiency versus pH. See bulleted list in
text for
explanation of
the legend.
4
Figures S4 and S5
analyze reported longevity.
Figure
S4
shows the reported longevity
sorted
by
device type. The devices with isolated PV elements tend to have
longer reported lifetimes, but
there are very few demonstrations exceeding
one week in
duration. Figure 5 graphs reported
longevity versus the
pH of
the electrolyte.
Again, there are very few reports of long-term device
operation at any electrolyte pH. Three studies have reported a lifetime over
100 hr.
Two of
those used a 3J with isolated PV
elements and the
other employed 3 PV junctions
with one being
an SLJ.
Figure S4
. Histogram
of the number of reports for each lifetime range, organized by device configuration.
The
studies that did not
report a
lifetime were not included in the figure above.
5
Figure S5
.
Reported lifetime in hours graphed versus
pH. See bulleted list in
text for explanation of the legend.