of 31
nature energy
https://doi.org/10.1038/s41560-023-01302-y
Artic�e
Understanding hydrogen electrocatalysis by
probing the hydrogen-bond network of
water at the electrified Pt–solution interface
In the format provided by the
authors and unedited
1
Table of contents
Supplementary Tables ................................................................................................. 2
Supplementary Figures ................................................................................................
4
Supplementary Notes
.
...............................................................................................
14
Supplementary Refer
ences ..........................................................................................
3
0
2
Supporting Tables
Supplementary
Table
1
.
Summary
of
the
specific exchange current densities (
i
0
,
iR
-
corrected) of Pt/C (8
μg
Pt
·cm
-
2
) with or without 10
-
5
M
organic compounds
in H
2
-
saturated 0.1 M KOH with a rotation rate of
2,500 rpm and
a
scan rate of 20 mV·s
-
1
, room temperature
.
i
0
(mA·cm
-
2
Pt
)
Additive
Notion
0.1 M KOH
0.1 M KOH + 10
-
5
M
additive
Caffeine
Caffeine
0.63
0.89
1,3
-
dimethyluracil
1,3
-
dimethyluracil
0.62
0.63
Imidazole
Imidazole
0.66±0.01
0.68±0.03
1
-
methylimidazole
Me
-
N
1
0.61±0.01
0.83±0.03
2
-
methylimidazole
Me
-
C
2
0.65±0.01
0.84±0.03
4
-
methylimidazole
Me
-
C
4
0.64±0.03
0.73±0.04
2,4
-
dimethylimidazole
Me
-
C
2,4
0.60±0.01
0.79±0.02
1,2
-
dimethylimidazole
Me
-
N
1
C
2
0.65±0.02
1.02±0.03
*
The standard deviation
is
based on
at least three independent measurements.
Supplementary
Table 2
.
Su
mmary of the
Natural Bond Orbital
calculation
results
of
the charge of the N
3
in
the
N
-
methylimidazoles
listed
.
Compound
N
1
charge
N
3
charge
Calculated N
3
charge
Imidazole
-
0.503
-
0.519
-
0.511*
Me
-
N
1
-
0.349
-
0.523
-
0.523
Me
-
C
2
-
0.508
-
0.529
-
0.519*
Me
-
C
4
-
0.504
-
0.526
-
0.517*
Me
-
C
5
-
0.507
-
0.521
-
0.51
3
*
Me
-
C
2,4
-
0.510
-
0.535
-
0.524*
Me
-
C
2,5
-
0.513
-
0.531
-
0.52
1
*
Me
-
N
1
C
2
-
0.353
-
0.530
-
0.530
*N
3
charges are averaged
by considering the
proton exchange effect
between N
1
and N
3
.
As
for imidazole
and Me
-
C
2
, the N
3
charge is obtained by averaging the charge of the N
1
and N
3
in the same compound
since they are equivalent in these two compounds.
As
for Me
-
C
4
and Me
-
C
2,4
, the N
3
charge is obtained
by averaging the charge of N
3
and the ch
arge of N
1
of their tautomer Me
-
C
5
and Me
-
C
2,5
, respectively,
since
the N
1
of Me
-
C
5
and Me
-
C
2,5
is essentially the N
3
of
Me
-
C
4
and Me
-
C
2,4
but with a proton.
(
D
etails
given Supplementary Note 1).
No
proton exchange
for
Me
-
N
1
and Me
-
N
1
C
2
since their N
1
is occupied by
a methyl group.
3
Supplementary
Table 3
.
Summary of the
NMR results of six N
-
methylimidazoles in 0.1 M KOH with
10% D
2
O+ 90% H
2
O (noted as 0.1 M KOH) and in 10% CD
2
Cl
2
+ 90% CH
2
Cl
2
(noted as CH
2
Cl
2
)
N
3
c
hemical shift
(ppm)
N
3
chemical shift change (ppm)
Compound
0.1 M KOH
CH
2
Cl
2
Imidazole
209.5
214.6
5.1
Me
-
N
1
249.9
265.3
15.4
Me
-
C
2
206.5
212.9
6.4
Me
-
C
4
204.3
214.5
10.2
Me
-
C
2,4
198.8
209.4
10.6
Me
-
N
1
C
2
246.1
262.2
16.1
Supplementary
Table 4
.
Summary of the
bond distances
of the parallel configuration of
Me
-
N
1
C
2
and
the interfacial water in the first two layers
on 0
e
-
and 3
e
-
Pt(100) surfaces
calculated
from time
-
averaged
AIMD
trajectory for 10 ps
.
The bond distances of the configuration
abse
nt of
Me
-
N
1
C
2
on the 3 e
-
Pt(100)
surface are included as a baseline for comparison.
Bond distance
(Å)
H
2
O(H
-
up)
1st
-
Pt
&
H
2
O(H
-
down)
1st
-
Pt
&
H
2
O(H
-
down)
2nd
-
Pt
&
N
3
···H
*
Pt
-
N
*
Pt
-
C
*
Pt
surf
-
CH
3
0 e
-
(acidic)
2.21
3.14
3.54
2.30
2.07
2.34
2.08
2.17
2.93
3.20
3 e
-
(alkali)
-
3.14
3.68
1.73
2.08
2.17
2.07
2.13
2.90
3.11
3 e
-
(No Me
-
N
1
C
2
)
-
3.28
4.
34
-
-
-
-
*
denotes t
he distance
s
between two atoms.
&
denotes that those values
are
calculated from z
-
axis distribution function (ZDF)
of oxygen atoms with
respect to the Pt surface
.
Supplementary
Table
5
.
Summary
of the
relative
total
energ
y
of the
parallel and vertical
configutions
of
Me
-
N
1
C
2
with respective to that of the
Me
-
N
1
C
2
in the
second layer
(all three configurations are
displayed in Figure S10
)
on 0
e
-
and 3
e
-
Pt(100) surfaces
calculated from 10 ps
AIMD
.
Relative
energy (eV)
2
nd
layer
Vertical
Parallel
0
e
-
0
-
1.32
-
2.21
3
e
-
0
-
0.51
-
0.82
4
Supporting Figures
Supplementary
Fig
ure
1
.
The
HOR/HER curves (
iR
-
corrected, cathodic)
of Pt/C (8 μg
Pt
·cm
-
2
) with or
without 10
-
5
M (
a
) caffeine, (
b
) 1,3
-
dimethyluracil, (
d
) imidazole and (
c
,
f
-
i
)
N
-
methylimidazole
s
in H
2
-
saturated 0.1 M KOH with a rotation rate of 2,500 rpm and a scan rate of 20 mV·s
-
1
, room temperature.
The structure of
the
corresponding compound
is given in the inset. (
e
) illustrates the atomic numbering of
the imidazole ring, an
d the R
1,2,3
represents possible location(s) for methyl group(s).
-0.05
0.00
0.05
0.10
0.15
0.20
-10
-8
-6
-4
-2
0
2
4
i (mA cm
-2
disk
)
Potential (V vs RHE)
0.1 M KOH
+ 10
-5
M Me-C
2,4
-0.05
0.00
0.05
0.10
0.15
0.20
-10
-8
-6
-4
-2
0
2
4
i (mA cm
-2
disk
)
Potential (V vs RHE)
0.1 M KOH
+ 10
-5
M 1,3-dimethyluracil
b
-0.05
0.00
0.05
0.10
0.15
0.20
-10
-8
-6
-4
-2
0
2
4
i (mA cm
-2
disk
)
Potential (V vs RHE)
0.1 M KOH
+10
-5
M caffeine
a
-0.05
0.00
0.05
0.10
0.15
0.20
-10
-8
-6
-4
-2
0
2
4
i (mA cm
-2
disk
)
Potential (V vs RHE)
0.1 M KOH
+ 10
-5
M Me-N
1
C
2
i
-0.05
0.00
0.05
0.10
0.15
0.20
-10
-8
-6
-4
-2
0
2
4
i (mA cm
-2
disk
)
Potential (V vs RHE)
0.1 M KOH
+ 10
-5
M Me-C
2
g
h
-0.05
0.00
0.05
0.10
0.15
0.20
-10
-8
-6
-4
-2
0
2
4
i (mA cm
-2
disk
)
Potential (V vs RHE)
0.1 M KOH
+ 10
-5
M Me-C
4
f
-0.05
0.00
0.05
0.10
0.15
0.20
-10
-8
-6
-4
-2
0
2
4
i (mA cm
-2
disk
)
Potential (V vs RHE)
0.1 M KOH
+10
-5
M imidazole
d
e
-0.05
0.00
0.05
0.10
0.15
0.20
-10
-8
-6
-4
-2
0
2
4
i (mA cm
-2
disk
)
Potential (V vs RHE)
0.1 M KOH
+ 10
-5
M Me-N
1
c
5
Supplementary
Fig
ure
2
.
The c
yclic voltammograms (
CV
s) of Pt/C (8 μg
Pt
·cm
-
2
) with or without 10
-
5
M
(
a
) imidazole, (
b
)
Me
-
C
4
, (
c
)
Me
-
C
2
, (
d
)
Me
-
C
2,4
, (
e
)
Me
-
N
1
,
and (
f
)
Me
-
N
1
C
2
in Ar
-
saturated 0.1 M KOH
with a scan rate of
2
0 mV·s
-
1
, room temperature.
Supplementary
Fig
ure
3.
The
CV
s (
a, c
) and
iR
-
corrected
HER/HOR polarization curves (
b, d
) of Pt
electrodes in Ar/H
2
-
saturated 0.1 M KOH
with/without 10
-
5
M imidazole (top) or 1,3
-
dimethyluracil
(bottom)
.
The polarization curves displayed in (b, d) were collected by scanning the RDE electrode from
0.9 V to
-
0.2 V with a scan rate of 20 mV·s
-
1
and a rotation rate of 2,500 rpm at room temper
ature.
0.0
0.2
0.4
0.6
0.8
1.0
-0.2
-0.1
0.0
0.1
0.2
i (mA cm
-2
disk
)
Potential (V vs RHE)
0.1 M KOH
+ 10
-5
M Me-C
2
c
0.0
0.2
0.4
0.6
0.8
1.0
-0.3
-0.2
-0.1
0.0
0.1
0.2
0.3
i (mA/cm
2
disk
)
Potential (V vs RHE)
0.1 M KOH
+ 10
-5
M imidazole
a
0.0
0.2
0.4
0.6
0.8
1.0
-0.2
-0.1
0.0
0.1
0.2
i (mA cm
-2
disk
)
Potential (V vs RHE)
0.1 M KOH
+ 10
-5
M Me-N
1
C
2
f
0.0
0.2
0.4
0.6
0.8
1.0
-0.2
-0.1
0.0
0.1
0.2
i (mA cm
-2
disk
)
Potential (V vs RHE)
0.1 M KOH
+ 10
-5
M Me-C
2,4
d
0.0
0.2
0.4
0.6
0.8
1.0
-0.2
-0.1
0.0
0.1
0.2
i (mA cm
-2
disk
)
Potential (V vs RHE)
0.1 M KOH
+ 10
-5
M Me-C
4
b
0.0
0.2
0.4
0.6
0.8
1.0
-0.2
-0.1
0.0
0.1
0.2
i (mA cm
-2
disk
)
Potential (V vs RHE)
0.1 M KOH
+ 10
-5
M Me-N
1
e
0.0
0.2
0.4
0.6
0.8
1.0
-0.3
-0.2
-0.1
0.0
0.1
0.2
0.3
i (mA cm
-2
disk
)
Potential (V vs RHE)
0.1 M KOH
+ 10
-5
M imidazole
a
-0.05
0.00
0.05
0.10
0.15
0.20
-10
-8
-6
-4
-2
0
2
4
i (mA cm
-2
disk
)
Potential (V vs RHE)
0.1 M KOH
+10
-5
M imidazole
b
-0.05
0.00
0.05
0.10
0.15
0.20
-10
-8
-6
-4
-2
0
2
4
i (mA cm
-2
disk
)
Potential (V vs RHE)
0.1 M KOH
+ 10
-5
M 1,3-dimethyluracil
d
0.0
0.2
0.4
0.6
0.8
1.0
-0.3
-0.2
-0.1
0.0
0.1
0.2
0.3
I (mA cm
-2
)
Potential (V vs RHE)
0.1 M KOH
+ 10
-5
M 1,3-dimethyluracil
c