of 1
Supplementary Information for:
Hydrogen Evolution Characteristics of
Ni
Mo
-
Coated Radial
Junction n
+
p
Silicon Microwire Array Photocathodes
Emily L. Warren,
a
James R. McKone,
a
Harry A. Atwater,
bc
Harry B. Gray
,
a
and Nathan S. Lewis
*ac
a
Division of Chemistry and Chemical Engineering,
b
Thomas J. Watson Laboratories of Applied Physics,
c
Kavli
Nanoscience Institute, California Institute of Technology, 1200 E. California Blvd, Pasadena, CA 91125
Comparing Galvanostatic and
Potentiostatic
deposition
of
Ni
Mo
Figure S1 shows the
J
-
E
performance for
two
nominally identical radial n
+
-
p junction SiMW
electrodes with
Ni
Mo
deposited by galvanostatic
(red)
and
potentiostatic
(blue)
cond
it
ions
,
respectively
. The electrodes were made without any
scattering particles, and thus produced lower
J
sc
values then the champion devices.
Figure S1
:
J
-
E
data for n
+
p
-
Si MW array
photocathodes measured in H
2
-
purged pH 4.5 KHP
buffer under ELH
-
type solar illumination. The data
in red
are
for
Ni
Mo
deposited under galvanostatic
conditions, and the data in blue for
Ni
Mo
deposited
potentiostatically. The
J
-
E
data
are
referenced to the
reversible hydrogen
evolut
ion
potential in the
solution (
E
(H
+
/H
2
) =
-
0.51 V vs. SCE).
The effect of electrolyte on catalytic activity
Figure S
2
shows a comparison of H
2
generation at a Pt electrode in 0.5
M H
2
SO
4
and pH
4.5 KHP buffer. The onset of catalytic activity is not
as
rapid
at neutral pH
,
due to the change in
mechanism of the HER at the
different
pH
conditions.
Figure S
2
: Comparison of Pt electrode in pH 4.5
KHP and 0.5 M H
2
SO
4
(pH=
0). Data w
ere
collected
using linear sweep voltammetry at 20 mV
s
-
1
. Prior
to data collection, the Pt working electrode was
repeatedly
cycled between
-
0.2 V and +1.2 V versus
RHE to clean
the Pt surface
.
Electronic Supplementary Material (ESI) for Energy & Environmental Science
This journal is © The Royal Society of Chemistry 2012