Noncovalent immobilization of Co(ii)porphyrin through axial coordination as an enhanced electrocatalyst on carbon electrodes for oxygen reduction and evolution

Article abstract of DOI:10.1039/c9nj02408e

Catalysis of fuel-producing reactions can be transferred from homogeneous solution to a surface via attachment of the molecular catalyst. A pyrene-pyridine hybrid (Py-Py) was used as an axial ligand to bridge Co(ii)tetraphenylporphyrin which was finally immobilized on carbon nanotubes via noncovalent interactions and further deposited on glassy carbon. This noncovalent immobilization of Co(ii)porphyrin through axial coordination provides significantly enhanced electrochemically catalyzed oxygen reduction and oxygen evolution, illustrating a new insight into understanding surface catalysis.

Full text of DOI:10.1039/c9nj02408e

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Noncovalent Immobilization of Co(II)porphyrin through Axial
Coordination as an Enhanced Electrocatalyst on Carbon Electrode
for Oxygen Reductions and Evolutions
Received 00th January 20xx,
Accepted 00th January 20xx
Isaac Kwaku Attatsia, Weihua Zhua,b* and Xu Lianga,b
*
DOI: 10.1039/x0xx00000x
Catalysis of fuel-producing reactions can be transferred from homogeneous solution to surface via attachment of the
molecular catalyst. A pyrene-pyridine hybrid (Py-Py) was used as an axial ligand to bridge Co(II)tetraphenylporphyrin which
was finally immobilized on carbon nanotubes via noncovalent interactions and further deposited on glassy carbon. This
noncovalent immobilization of Co(II)porphyrin through axial coordination provides significantly enhanced electrochemically
catalyzed oxygen reductions and oxygen evolutions, illustrating a new insight into understanding surface catalysis.
electrocatalyst for ORR derived from a cobalt porphyrin-based
covalent organic framework 25. Sonkar and co-workers also
synthesized different kinds of substituted cobalt porphyrins and
Introduction
The ever-growing demands for fossil fuels accompanied by
increasing environmental pollutions emanating from fossil
depletion has been a matter of concern to researchers 1–3. This
resulted to an extensive search for a new renewable energy
source that is clean, cheap and efficient with zero emission.
15
compared their ORR activities to simple cobalt porphyrin
.
Maurin and Robert did noncovalent immobilization of a
molecular metalloporphyrin electrocatalyst using carbon
electrodes towards CO2 conversion 26. From their work a
pyrene-appended iron porphyrin bearing OH groups on phenyl
rings was immobilized on carbon nanotubes via noncovalent
interactions. Their work showed enhanced catalytic
performance. Based on these previous works, we selected a
medium that is most appropriate to further enhance the
electrocatalytic behaviour when coordinated to the metal
centre of porphyrin with stability of the system in mind. This led
to synthesis of 1 and Py-Py compound which when axially
bonded could effectively improve the catalytic performance of
our system on MWCNT support. In other to investigate this, we
Technological advancement into energy production led to
4–7
development of fuel cells such as metal-air batteries
,
microbial fuel cells 8,9, direct solar driven water splitting 10–14 and
other forms of regenerative fuel cells. Oxygen reduction and
evolution (ORR and OER) play an important role in these various
renewable energy conversion systems. To this extent the
designing and development of catalysts for ORR and OER are at
the heart of researchers towards the advancement of
renewable energies. Traditionally, Pt based catalysts and oxides
of other noble metals of Iridium and ruthenium are employed
herein
report
a
new
strategy
to
construct
15
in ORR and OER respectively
but are limited due to low
metallopophyrin@MWCNTs nanocomposite with pyrene-
pyridine hybrid (Py-Py) used as an axial ligand to bridge
Co(II)tetraphenylporphyrin which was finally immobilized on
carbon nanotubes via noncovalent interactions and further
deposited on glassy carbon. Comparatively, the enhanced
electrocatalytic behaviour shown by 1/MWCNT/Py-Py is as a
result of the axial ligand system (Py-Py) coordinated to
Co(II)tetraphenylporphyrin. This means rationally tuning the
electrocatalytic environment instead of the active catalytic
center is a promising strategy to improve ORR and OER.
natural abundance and high cost. Methanol poisoning arising
from Pt based catalyst is another ground to look for safer and
highly desirable catalyst for ORR and OER. The development of
low cost and earth abundant 3d transition metals of Co, Ni, Mn
and Fe catalysts offer a promising route to compete with
platinum barometer 16–20. Metalloporphyrins with their high
catalytic properties are increasingly being modified and
rationally designed to effectively serve as a means of reducing
21–23
or evolving oxygen
in fuel cells. Zhang and co-workers
reported cobalt porphyrins functionalized on carbon support is
effective for ORR 24. Mao and co-workers reported an efficient
Experimental
Functionalization of MWCNTs
a
School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang
212013, P. R. China. E-mail: liangxu@ujs.edu.cn, Tel@Fax: +86-511-8879-1928 (to
X. L.); E-mail: sayman@ujs.edu.cn, Tel@Fax: +86-511-8879-1928 (to W. Z.)
b
State Key Laboratory of Coordination Chemistry, Nanjing University, Nanjing
210000, P. R. China
† Footnotes relating to the title and/or authors should appear here.
Electronic Supplementary Information (ESI) available: [details of any supplementary
information available should be included here]. See DOI: 10.1039/x0xx00000x
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Scheme 1. Synthesis of Co(II)porphyrin (1) and pyrene-pyridine hybrid (Py-Py).
A known mass of 2.0 mM Py-Py was mixed with 5.0 mg
Results and discussion
Structural Characterization
MWCNT and sonicated for 30 min in 5 mL isopropyl alcohol (IPA)
nafion mixture. The mixture was stirred for 24 h, filtered and
washed. It was dried under vacuum for 24 h and labelled
MWCNT/Py-Py composite. 1mg of the composite was measured
and mixed with 1 mL IPA and sonicated for 30 min. After 1.0 mM
co(II)porphyrin was added to the surfaced modified MWCNTs
IPA solution and the mixture stirred for 12 h at room
temperature. This composite material was filtered, washed with
5 mL IPA (to remove any weakly adsorbed Co(II)porphyrin),
dried under vacuum and labelled as 1/MWCNT/Py-Py. The
unfunctionalized MWCNTs (1.0 mg) were also mixed with
Co(II)porphyrin (1.0 mM) at same reaction conditions and
process to give 1/MWCNT. The prepared materials
(1/MWCNT/Py-Py and 1/MWCNT) were used for SEM, XRD, UV,
FT-IR and EPR characterizations.
The morphology of MWCNT, 1/MWCNT, MWCNT/Py-Py
and 1/MWCNT/Py-Py composites were confirmed by using
scanning electron microscopy. As shown in Figure 1, the
nanotubes appeared visibly clear with a uniform capsule-like
morphology. Nodular topography with less or no aggregation as
seen in Figure 1 illustrates uniform distribution of 1 on the
surface of the MWCNT 31,32. This appearance was similar in
1/MWCNT, MWCNT/Py-Py and 1/MWCNT/Py-Py composites.
As shown in Figure 2a, powder x-ray diffraction (XRD) patterns
of MWCNT showed two diffraction signals at 2θ = 25.8o and
43.3o which corresponds to MWCNT structure
Characteristic features of 1 were exhibited at 2θ = 25.8o and
45.0o (weak) in 1/MWCNT and 1/MWCNT/Py-Py which is in line
with metalloporphyrin XRD patterns. Composite materials of
33,34
.
Electrode Modification
1/MWCNT and 1/MWCNT/Py-Py maintained
diffraction signal at 2θ = 25.8o which illustrates the graphitic
nature of MWCNT is retained
a strong
A 2 µL suspension of the composite (MWCNT/Py-Py) was
drop coated on surface of glass carbon electrode (GC) thrice and
allowed to dry for 2 h. Prior to drop coating of composite onto
GC, the surface was polished with 0.05 µm alumina and rinsed
with doubly distilled water in ultrasonic bath to remove any
adhered Al2O3 particles. It was rinsed with ethanol and dried
under room temperature for about 10 min. The modified GC
electrode (GC/MWCNT/Py-Py) was immersed in a 1.0 mM
CH2Cl2 solution of 1 (Co(II)porphyrin) and stored for 12 h to
achieve coordination to the metal centre of the porphyrin. The
modified electrode was removed from the Co(II)porphyrin
solution, dried and washed with 5 mL CH2Cl2 until almost
colourless solution was observed. The washing was to purposely
remove any weakly adsorbed Co(II)porphyrin 27–31. It was air
dried for 1-2 h, labelled as 1/MWCNT/Py-Py and ready for ORR
and OER experiments. Steps and processes to obtain
GC/MWCNT with immobilized Co(II)porphyrin (1/MWCNT) is
similar to 1/MWCNT/Py-Py with difference in absence of Py-Py
moiety.
35
. The appearance of
characteristic peaks at 45.0o (111) indicates the Co(II)porphyrin
is completely encapsulated within the graphitic carbon 36. It is
worthy to note that weak diffraction feature of cobalt could
occur, and this is when the mass of 1 in the composites is low or
the temperature applied to composite before characterization
is not strong enough 37. UV-vis spectra of 1 revealed an intense
Soret band peak at
λ= 409 nm whereas Q band absorptions
appeared at = 526 nm (Fig. 2b). Coordination interactions
λ
between 1 and Py-Py, were firstly investigated in CH2Cl2 devoid
of carbon nanotubes as shown in Fig. S4. The Co(II)porphyrin
peaks were retained at 409 nm and 526 nm with emergence of
Py-Py peak between 300-350 nm indicating a week interaction.
Also noted is a weak peak at 433 nm which might be the source
of 1 and Py-Py coordination. In other to understand this
interaction further, we compared the UV-Vis absorption spectra
of 1/Py-Py to that of 1 and pure pyridine mixture. As shown in
the spectra, addition of microliters of pyridine introduces peaks
at 433 nm same as that of 1/Py-Py.
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Figure 1. SEM images of MWCNT (a), 1/MWCNT (b),
MWCNT/Py-Py (c) and 1/MWCNT/Py-Py (d) materials.
Figure 2. XRD patterns (a), UV-Vis absorption spectra in
CH2Cl2 (b), EPR (c), and FT-IR (d) of composites.
This therefore is a clear evidence the metal center of 1
coordinated through the pyridine of our Py-Py, on its axial MWCNT (Fig. S5, top) showed a strong and broad band around
positions. Composite materials from 1/MWCNT and 3425ꢀcm−1 attributed to the presence of -OH or -COOH
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1/MWCNT/Py-Py were also characterized using UV-Vis functional group and a very weak band at 1545 cm-1 in the
spectroscopic technique. Spectra of the 1/MWCNT showed a fingerprint region attributed to C=C vibrations. 1/MWCNT (Fig.
slight shift of Soret band to
λ= 415 nm. This indicates an S5, bottom) composite showed characteristic strong and broad
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interaction between 1 and MWCNTs which also confirmed band at 3430 cm-1 showing presence of -OH or -COOH
the presence of metallic cobalt through XRD analysis. In the case emanating from MWCNT. A weak band that appeared at 3052
of 1/MWCNT/Py-Py composite, a larger red-shift of the cm-1 results from the C-H stretching in phenyl ring of 1 while
absorptions has been observed in both Soret (433 nm) and Q that of 2931 cm-1 represents symmetric and antisymmetric alkyl
bands (545 nm) regions indicating an interaction between C-H vibrations of the porphyrin ring 45. Peaks at 1596 cm-1 (C=C
MWCNT, 1 and Py-Py. It is important to reiterate that the Py-Py stretching vibrations of phenyl rings) 46, 1349 cm-1 (C-N), 1076
linker serves as a coordination ligand responsible for axial cm-1 (C=C symmetric stretching of pyrrole ring), 1003 cm-1 (C-C
coordination to the cobalt centre 38,39. The appearance of a new vibrations of pyrrole ring) 47, 703 cm-1 (C-N) and 750 cm-1 (C-N
soret peak of 1/MWCNT/Py-Py without appearance of out of plane bending)47 are all characteristic peaks of 1. The
1/MWCNT peaks indicates all 1 has been coordinated with Py- presence of these peaks provides evidence of 1 in the
Py 40 as shown in the (Fig. 2b). Spectra for 1/MWCNT/Py-Py (Fig. composite mixture (1/MWCNT). Spectra from Py-Py, Py-
2b) further explains changes in geometrical symmetry and Py/MWCNT, and 1 all appeared in 1/MWCNT/Py-Py (Fig. 2d).
electronic density 41 of 1 upon introduction of Py-Py which is as The appearance of 1 and Py-Py peaks in this spectrum confirms
a result of axial coordination of py-py towards the Co (II) ion of the formation of the composite 48 an indication that all products
29,42,43. This was also demonstrated by solid state electron have been successfully intercalated. This also further proves the
paramagnetic resonance (EPR) spectra of nanocomposites presence of metallic cobalt in our composite materials as
where 1/MWCNT/Py-Py nanocomposite has revealed indicated with black dotted lines. It is worthy to note that the
decreased magnetic field strength value compared with addition of 1 to Py-Py/MWCNT showed no change in peak
1/MWCNT that clearly reflected the changes of coordination positions of 1 indicating there was a little or no change in
environment. FTIR spectra of our composite materials are functional group during adsorption.
shown in Fig. 2d (1/MWCNT/Py-Py) and Fig. S5 (1/MWCNT).
1
a
Table1: CV comparisons of ORR activities of 1/MWCNT/Py-Py and 1/MWCNT in different aqueous solutions.
Onset potential
for ORR
(V vs RHE)
+ 0.584
Current
densities
(mA.cm−2)
10.07
4.53
3.732
0.771
0.939
0.665
Aqueous
media
Peak potential
(V vs RHE)
Catalyst
1/MWCNT/Py-Py
H2SO4
PBS
+ 0.375
+ 0.253
+ 0.766
+ 0.203
+ 0.222
+ 0.701
+ 0.512
KOH
H2SO4
PBS
+ 0.890
+ 0.583
+ 0.519
+ 0.880
1/MWCNT
KOH
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LSV as shown in Fig. 3c. This is an indication of 1/MWCNT/Py-
View Article Online
Py showing high ORR catalytic efficieDnOcyI: 1a0s.103c9o/mC9pNaJr0e2d40t8oE
1/MWCNT. Sonkar and co-workers also tested ORR in acidic
medium for three different kinds of cobalt porphyrins whose
observed onset potentials were E = + 0.43, + 0.44 and + 0.49 V
for MWCNT/CoTPP, MWCNT/CoTCPP and MWCNT/CoTHPP
respectively with lower corresponding current densities 15. The
onset potentials, peak potentials, and current densities
presented herein for 1/MWCNT/Py-Py are by far greater than
theirs in acidic medium under similar conditions. Comparison
was further extended to commercial 20 wt% platinum–carbon
(Pt/C) catalysts which is reported to show an onset at E = + 0.88
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V
15 which is more positive than our work. Despite high onset,
the limiting current density for the 1/MWCNT/Py-Py moiety is
by far 10.07 mA.cm−2 greater as appeared in the CV curve for
15
the Pt/C
when the electrolyte was saturated with O2,
Figure 3. CVs of GC electrodes coated with (a)
1/MWCNT/Py-Py, (b) 1/MWCNT and (c) LSV of GC
electrodes coated with 1/MWCNT/Py-Py and 1/MWCNT
under N2 or O2 in 0.5 M H2SO4(aq). Conditions: 50 mV s–1
scan rate at 25 °C.
suggesting a pronounced catalytic activity for our catalyst
towards ORR. This means the 1/MWCNT/Py-Py materials could
serve as an alternative to the expensive Pt/C catalyst under
similar conditions. CV data of different scan rates (10–400 mVs-
1) at 1/MWCNT/Py-Py electrode in 0.5 M H2SO4 showed
increase in anodic and cathodic peak currents (Fig. 4a). A plot of
the peak current vs. square root of scan rate (Fig. 4b) shows a
linear relationship (R
=
0.98) which indicates the
electrochemical process is diffusion controlled 49. Oxygen
reduction reaction activities were also monitored in various pH
values, such as PBS (pH ≈ 7) and KOH (pH ≈ 14). It was clearly
demonstrated the onset potentials of the two materials
(1/MWCNT/Py-Py and 1/MWCNT) are similar but there
appears a great difference in current densities. 1/MWCNT/Py-
Py pronounced an outstanding catalytic performance toward
ORR more than 1/MWCNT in both solutions as shown in LSV
data (Fig. 5a and 5b).
Figure 4. CV response of 1/MWCNT/Py-Py at different scan
rates (a) Plot of anodic and cathodic peak currents vs
square roots of scan rate (b) in 0.5 M H2SO4 solution.
Electrochemically Catalyzed ORRs
Electrochemically catalysed oxygen reduction reaction is an
important reaction since it is one of the key determinants for
realization of hydrogen-based society. In the current study,
cyclic voltammetry (CV) was firstly carried in 0.5 M H2SO4 (pH ≈
0) to examine the ORR catalytic activity of 1 axially linked Py-Py
on MWCNT (1/MWCNT/Py-Py) support at a scan rate of 50 mV
−1
s
(Fig. 3a). Under N2 atmosphere, the CV curve within the
Figure 5. LSV of GC electrodes coated with 1/MWCNT/Py-Py and
1/MWCNT under O2 in (a) 1.0 M KOH and (b) 0.1 M PBS.
Conditions: 50 mV s–1 scan rate at 25 °C.
scanned potential ranges presented almost featureless slope
for the cathodic current. In a sharp contrast, an explicit positive
peak potential of + 0.375 V and a high and stable current density
at 10.07 mA.cm−2 were observed with an onset at + 0.584 V.
Comparisons were made between a direct 1 self-assembled on
CV data (Fig. S6 and S7) obtained showed similar result as
GC electrode with MWCNT support (Fig. 3b) and 1/MWCNT/Py- that of LSV in both aqueous solutions. The onset potentials,
Py. We observed that although the onset potentials were peak potentials and current densities are all summarized in
similar, there was a great difference by more than 5 times in the Table 1. The stability of the materials (1/MWCNT/Py-Py and
current densities. While 1/MWCNT showed current density at 1/MWCNT) were investigated in H2SO4(aq). This was studied
0.77 mA.cm−2, 1/MWCNT/Py-Py exhibited an outstanding when substrates used earlier for CV and LSV experiments in
catalytic peak with current density of 10.07 mA.cm−2. Also, the acidic medium were washed with several milliliters of CH2Cl2
peak potentials of 1/MWCNT were observed at E = + 0.203 V and LSV experiment run again. They all showed subtle stability
which is less positive than 1/MWCNT/Py-Py whose peak in acidic medium as illustrated in Figure 6.
potential was E = + 0.375 V. This similar trend was observed in
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mV 50. In our work at j = 1.0 mA.cm-2 an onset overpotential of
400 mV was recorded which is quite better than works of Wang
View Article Online
DOI: 10.1039/C9NJ02408E
and co-workers, another evidence of enhanced activity of
1/MWCNT/Py-Py compared to 1/MWCNT. Surface stability of
our materials were checked after rinsing with CH2Cl2 and
subjected to electrocatalytic OER activity. The results as shown
in Fig. 7c indicates the rinsed 1/MWCNT/Py-Py lost activity of
about 8% while 1/MWCNT lost activity of about 4% (Fig. 7d).
LSV (Fig. 8a) data obtained in KOH showed a much higher
catalytic activity than those exhibited in PBS. In addition, at j =
10 m. Acm-2 an onset overpotential of 440 mV was recorded at
an onset of 1.67 V for 1/MWCNT/Py-Py which is smaller than
480 mV recorded for 1/MWCNT at same j value. Comparing the
onset overpotentials for 1/MWCNT/Py-Py in both PBS and KOH,
the latter is highly recommended since OER catalysis is more
enhanced.
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Figure 6. LSVs of GC electrodes coated with (a)
1/MWCNT/Py-Py and (b) 1/MWCNT in 0.5 M H2SO4 (aq)
solution before and after rinsing with 5 mL CH2Cl2.
Conditions: 50 mV s–1 scan rate at 25 °C.
Electrochemically Catalyzed OERs
In other to investigate the OER activity of 1 on MWCNT/Py-
Py and MWCNT, CV experiments were carried out in 0.1 M PBS
and 1.0 M KOH. In PBS, 1/MWCNT/Py-Py displayed a very high
catalytic current at j = 45 mA.cm-2 (E = 2.6 V) with onset at 1.7 V
(Fig. 7a). 1/MWCNT with similar onset at 1.7 V displayed its
current density at j = 35 mA.cm-2. At j = 10 mA.cm-2, an onset
overpotential of 650 mV (Fig. 7a) was obtained for
1/MWCNT/Py-Py while that of 1/MWCNT was 790 mV (Fig. 7b).
It is worthy to note that the onset overpotential of
1/MWCNT/Py-Py is 140 mV less than 1/MWCNT an indication
that OER activity of 1/MWCNT/Py-Py is best owing to presence
of Py-Py.
Figure 8. LSVs of GC electrodes coated with (a) MWCNT,
1/MWCNT, MWCNT/Py-Py and 1/MWCNT/Py-Py in 1.0 M
KOH at 50 mV s–1 scan rate (b) Controlled-potential
electrolysis at E = +2.25 V (RHE) in 0.1 M PBS using GC
electrodes coated with 1/MWCNT and 1/MWCNT/Py-Py at
25 °C.
Controlled-bulk electrolysis was performed in 0.1 M PBS
using GC as a working electrode coated with 1/MWCNT/Py-Py,
Pt wire as the counter electrode and SCE as reference electrode.
The potential was set to E = (+2.25 V, RHE) and experiment run
for 240 min (Fig. 8b). The amount of O2 evolved could be seen
largely as bubbles on the electrode. That of 1/MWCNT is far less
compared to 1/MWCNT/Py-Py (Fig. 8b). Based on the results
presented in this work, we conclude that introduction of py-py
moiety which served as a linker is responsible for the enhanced
electrocatalyzed ORR and OER activities. The pyrene unit in the
py-py increased π-π staking interaction on carbon support.
Conclusions
In summary, A pyrene-pyridine hybrid (Py-Py) was used as an
axial ligand to bridge Co(II)tetraphenylporphyrin which was
finally immobilized on carbon nanotubes via noncovalent
interactions and further deposited on glassy carbon. This
noncovalent immobilization of Co(II)porphyrin through axial
coordination provides significantly enhanced electrochemically
catalysed oxygen reductions and oxygen evolutions. As a result,
our material (1/MWCNT/Py-Py) displayed a catalytic activity far
more than the ordinary 1/MWCNT in all media. The Py-Py
moiety served as a direct linker between the cobalt center of
the catalyst and MWCNT on electrode. This linker was
Figure 7. CVs of GC electrodes coated with (a)
1/MWCNT/Py-Py, (b) 1/MWCNT in 0.1 M PBS. (c)
1/MWCNT/Py-Py and (d) 1/MWCNT in 0.1 M PBS solution
before and after rinsing with CH2Cl2. Conditions: 50 mV s–1
scan rate at 25 °C.
OER activity of our material (1/MWCNT/Py-Py) was further
compared with the works of Wang and co-workers where
cationic cobalt porphyrin was used for OER. They reported OER
onset overpotential activity at j = 1.0 mA.cm-2 to a little over 400
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responsible for the enhanced electrocatalytic activities of our
material (1/MWCNT/Py-Py). In furtherance, the stability of
1/MWCNT/Py-Py indicates the strong nature of our system. We
can therefore conclude that the strategy of integrating active
molecular catalysts in rationally designed Py-Py combined with
MWCNT could enable new applications for molecular catalysts
in renewable fuel cells.
View Article Online
Chemistry, 1993, 357, 201–224.
DOI: 10.1039/C9NJ02408E
14 M. Li, L. Zhang, Q. Xu, J. Niu and Z. Xia, Journal of Catalysis, 2014,
314, 66–72.
15 P. K. Sonkar, K. Prakash, M. Yadav, V. Ganesan, M. Sankar, R.
Gupta and D. K. Yadav, Journal of Materials Chemistry A, 2017, 5,
6263–6276.
16 P. Du and R. Eisenberg, Energy & Environmental Science, 2012, 5,
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
6012–6021.
17 B. Reuillard, J. Warnan, J. J. Leung, D. W. Wakerley and E. Reisner,
Angewandte Chemie International Edition, 2016, 55, 3952–3957.
18 J. R. Galán‐Mascarós, ChemElectroChem, 2015, 2, 37–50.
19 W. Xia, A. Mahmood, Z. Liang, R. Zou and S. Guo, Angewandte
Chemie International Edition, 2016, 55, 2650–2676.
20 G. Wu, A. Santandreu, W. Kellogg, S. Gupta, O. Ogoke, H. Zhang,
H.-L. Wang and L. Dai, Nano Energy, 2016, 29, 83–110.
21 Q. Lin, X. Bu, A. Kong, C. Mao, X. Zhao, F. Bu and P. Feng, Journal
of the American Chemical Society, 2015, 137, 2235–2238.
22 A. Okunola, B. Kowalewska, M. Bron, P. J. Kulesza and W.
Schuhmann, Electrochimica Acta, 2009, 54, 1954–1960.
23 K. Kasahara, H. Tsuboi, M. Koyama, A. Endou, M. Kubo, C. A. Del
Carpio and A. Miyamoto, Electrochemical and solid-state letters,
2006, 9, A490–A493.
24 W. Zhang, A. U. Shaikh, E. Y. Tsui and T. M. Swager, Chemistry of
Materials, 2009, 21, 3234–3241.
25 W. Ma, P. Yu, T. Ohsaka and L. Mao, Electrochemistry
Communications, 2015, 52, 53–57.
26 A. Maurin and M. Robert, Journal of the American Chemical
Society, 2016, 138, 2492–2495.
Conflicts of interest
There are no conflicts to declare.
Acknowledgements
This work was financially supported by the National Natural
Science Foundation of China (project 21701058), the Natural
Science Foundation of Jiangsu province (project BK20160499),
the State Key Laboratory of Coordination Chemistry (projects
SKLCC1817), the Key Laboratory of Functional Inorganic
Material Chemistry (Heilongjiang University) of Ministry of
Education, the China post-doc foundation (No. 2018M642183),
the Lanzhou High Talent Innovation and Entrepreneurship
Project (No. 2018-RC-105) and the Jiangsu University (project
17JDG035, X. L.).
Notes and references
‡ supporting information is available via xxx
27 P. D. Tran, A. Le Goff, J. Heidkamp, B. Jousselme, N. Guillet, S.
Palacin, H. Dau, M. Fontecave and V. Artero, Angewandte
Chemie, 2011, 123, 1407–1410.
28 A. I. A. El-Mageed and T. Ogawa, Applied Surface Science, 2018,
462, 904–912.
1
2
Z. Shi, K. Nie, Z.-J. Shao, B. Gao, H. Lin, H. Zhang, B. Liu, Y. Wang,
Y. Zhang and X. Sun, Energy & Environmental Science, 2017, 10,
1262–1271.
Y. Wu, M. Chen, Y. Han, H. Luo, X. Su, M.-T. Zhang, X. Lin, J. Sun,
L. Wang and L. Deng, Angewandte Chemie International Edition,
2015, 54, 4870–4875.
29 Y. Zhou, Y. Shi, F.-B. Wang and X.-H. Xia, Analytical chemistry,
2019, 91, 2759–2767.
30 F. Li, B. Zhang, X. Li, Y. Jiang, L. Chen, Y. Li and L. Sun, Angewandte
Chemie International Edition, 2011, 50, 12276–12279.
31 X. Li, H. Lei, X. Guo, X. Zhao, S. Ding, X. Gao, W. Zhang and R. Cao,
ChemSusChem, 2017, 10, 4632–4641.
32 A. Rana, B. Mondal, P. Sen, S. Dey and A. Dey, Inorganic
chemistry, 2017, 56, 1783–1793.
33 T.-M. Wu and Y.-W. Lin, Polymer, 2006, 47, 3576–3582.
34 T. Zhao, C. Hou, H. Zhang, R. Zhu, S. She, J. Wang, T. Li, Z. Liu and
B. Wei, Scientific reports, 2014, 4, 5619.
3
4
5
W. Zhang, W. Lai and R. Cao, Chemical reviews, 2016, 117, 3717–
3797.
Y. Lee, J. Suntivich, K. J. May, E. E. Perry and Y. Shao-Horn, The
journal of physical chemistry letters, 2012, 3, 399–404.
B. Su, I. Hatay, A. Trojánek, Z. Samec, T. Khoury, C. P. Gros, J.-M.
Barbe, A. Daina, P.-A. Carrupt and H. H. Girault, Journal of the
American Chemical Society, 2010, 132, 2655–2662.
G. He, M. Qiao, W. Li, Y. Lu, T. Zhao, R. Zou, B. Li, J. A. Darr, J. Hu
and M. Titirici, Advanced Science, 2017, 4, 1600214.
F. Cheng and J. Chen, Chemical Society Reviews, 2012, 41, 2172–
2192.
K. Rabaey and W. Verstraete, TRENDS in Biotechnology, 2005, 23,
291–298.
M. Zhou, M. Chi, J. Luo, H. He and T. Jin, Journal of Power Sources,
2011, 196, 4427–4435.
35 J. Zhu, K. Kailasam, A. Fischer and A. Thomas, Acs Catalysis, 2011,
6
7
8
9
1, 342–347.
36 Z. Wu, L. Chen, J. Liu, K. Parvez, H. Liang, J. Shu, H. Sachdev, R.
Graf, X. Feng and K. Müllen, Advanced materials, 2014, 26, 1450–
1455.
37 Z. Sun, J. Li, H. Zheng, X. Liu, S. Ye and P. Du, International Journal
of Hydrogen Energy, 2015, 40, 6538–6545.
38 L. Ye, Y. Fang, Z. Ou, L. Wang, S. Xue, Y. Lu and K. M. Kadish,
Journal of Porphyrins and Phthalocyanines, 2019, 23, 196–205.
39 F. D’Souza, Y.-Y. Hsieh and G. R. Deviprasad, Inorganic chemistry,
1996, 35, 5747–5749.
40 G. F. Manbeck and E. Fujita, Journal of Porphyrins and
Phthalocyanines, 2015, 19, 45–64.
10 W. G. Hardin, D. A. Slanac, X. Wang, S. Dai, K. P. Johnston and K.
J. Stevenson, The journal of physical chemistry letters, 2013, 4,
1254–1259.
11 K. Xu, P. Chen, X. Li, Y. Tong, H. Ding, X. Wu, W. Chu, Z. Peng, C.
Wu and Y. Xie, Journal of the American Chemical Society, 2015,
137, 4119–4125.
12 J. R. McKone, S. C. Marinescu, B. S. Brunschwig, J. R. Winkler and
H. B. Gray, Chemical Science, 2014, 5, 865–878.
6 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 7 of 7
New Journal of Chemistry
Please do not adjust margins
Journal Name
41 M. A. Ehudin, L. B. Gee, S. Sabuncu, A. Braun, P. Moënne-Loccoz,
ARTICLE
1
2
3
4
5
6
7
8
View Article Online
DOI: 10.1039/C9NJ02408E
B. Hedman, K. O. Hodgson, E. I. Solomon and K. D. Karlin, Journal
of the American Chemical Society, 2019, 141, 5942–5960.
42 F. D’Souza, G. R. Deviprasad, M. E. Zandler, V. T. Hoang, A. Klykov,
M. VanStipdonk, A. Perera, M. E. El-Khouly, M. Fujitsuka and O.
Ito, The Journal of Physical Chemistry A, 2002, 106, 3243–3252.
43 J. Cao, D.-C. Hu, J.-C. Liu, R.-Z. Li and N.-Z. Jin, Journal of
Coordination Chemistry, 2013, 66, 4211–4219.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
44 H. Oshio, T. Ama, T. Watanabe, J. Kincaid and K. Nakamoto,
Spectrochimica Acta Part A: Molecular Spectroscopy, 1984, 40,
863–870.
45 L. Boucher and J. Katz, Journal of the American Chemical Society,
1967, 89, 1340–1345.
46 A. Salker and S. Gokakakar, Int. J of Phys Sci, 2009, 4, 377–3844.
47 D. R. Roy, E. V. Shah and S. M. Roy, Spectrochimica Acta Part A:
Molecular and Biomolecular Spectroscopy, 2018, 190, 121–128.
48 Z. Xu, H. Li, G. Cao, Q. Zhang, K. Li and X. Zhao, Journal of
Molecular Catalysis A: Chemical, 2011, 335, 89–96.
49 A. J. Bard, L. R. Faulkner, J. Leddy and C. G. Zoski, Electrochemical
methods: fundamentals and applications, Wiley New York, 1980.,
Wiley, New York, Wiley.
50 D. Wang and J. T. Groves, Proceedings of the National Academy
of Sciences, 2013, 110, 15579.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 7
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