H2 evolution catalyzed by a FeFe-hydrogenase synthetic model covalently attached to graphite surfaces

Article abstract of DOI:10.1039/c7cc04281g

A synthetic mimic of Fe-Fe hydrogenase (H₂ase) is reported which bears a terminal alkyne group in the ligand. Using a terminal azide bearing organic linkers, this complex could be covalently attached to various electrode surfaces (e.g. edge pla

Full text of DOI:10.1039/c7cc04281g

View Article Online
View Journal
ChemComm
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: Md. E. Ahmed, S.
Dey, B. Mondal and A. Dey, Chem. Commun., 2017, DOI: 10.1039/C7CC04281G.
This is an Accepted Manuscript, which has been through the
Volume 52 Number
1 4 January 2016 Pages 1–216
Royal Society of Chemistry peer review process and has been
accepted for publication.
ChemComm
Accepted Manuscripts are published online shortly after
Chemical Communications
www.rsc.org/chemcomm
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
author guidelines.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the ethical guidelines, outlined
in our author and reviewer resource centre, still apply. In no
event shall the Royal Society of Chemistry be held responsible
for any errors or omissions in this Accepted Manuscript or any
consequences arising from the use of any information it contains.
ISSN 1359-7345
COMMUNICATION
Marilyn M. Olmstead, Alan L. Balch, Josep M. Poblet, Luis Echegoyenet al.
Reactivity differences of Sc3N@C2n (2n 68 and 80). Synthesis of the
first methanofullerene derivatives of Sc N@D5h-C80
=
3
rsc.li/chemcomm

Please do not adjust margins
Page 1 of 4
ChemComm
View Article Online
DOI: 10.1039/C7CC04281G
Journal Name
COMMUNICATION
H2 Evolution Catalyzed by FeFe-Hydrogenase Synthetic Model
Covalently Attached to Graphite Surface
Md Estak Ahmed, Subal Dey, Biswajit Mondal and Abhishek Dey
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
www.rsc.org/
reaction.19-22 The advantage of covalent attachment via click
A synthetic mimic of Fe-Fe hydrogenase (H2ase) is reported which
bears a terminal alkyne group in the ligand. Using a terminal azide
bearing organic linkers, this complex could be covalently attached
to various electrode surfaces (e. g. – Edge Plane Graphite, reduced
Graphene oxide etc.). The electrocatalytic hydrogen evolution
(HER) efficiency of these construct is investigated and the results
show that EPG – H2ase mimic construct is able to produce H2 from
acidic water efficiently with over 90% selectivity.
reaction has been amply demonstrated in O2 reduction
catalysts.23 Functional models of cytochrome C oxidase and mono
nuclear Cu complex bearing a terminal alkyne group have been
covalently attached on electrode surfaces. But widely accepted
gold-thiol electrode construct is suitable for electro catalytic
investigations spanning mild potential ranges (0.5 to -0.5 V vs
Ag/AgCl), and is limited due to the instability of thiol SAM at highly
oxidizing/reducing potentials where the thiols gets desorbed.
Graphite on the other hand is a stable electrode material at highly
oxidizing and reducing potentials as well as over a wide range of
pHs. Thus covalent attachment of HER catalysts to graphite
electrodes is desirable. Till date there are only reports of covalent
attachment of H2ase mimic onto Au surface by Artero et. al.10, 24,
The increasing global energy demand and depleting fossil fuel-
reserves has generated keen interest in the development of
hydrogen (H2) based clean energy economy.1-3 There are several
molecular catalysts that are quite efficient to generate H2 in water
and most of them are directly adsorbed/deposited on various
electrodes and used as heterogeneous electrocatalysts.4-6 Only a
few catalysts have been covalently attached onto electrode
surfaces in a site specific manner.7-11 Site specific attachment
allows better replication of molecular catalysis under
heterogeneous condition.
25
The mimic investigated lacks the azadithiolato (ADT) bridge
which is proved to be necessary for enzymatic activity of Fe-Fe
H2ases.26 Here we are reporting the synthesis of an ADT bridged
p-alkynylbenzeneazadithiolate diironhexacarbonyl complex (
and its covalent attachment onto various (e. g. - rGO) electrode
surfaces. Prior to complex attachment, the electrodes have
A)
A
been modified with an azide terminated amine linker so that the
catalyst can be tethered on to the electrode surface by “click”
reaction. The inherent advantage of this modular approach is the
ability to modify the length of the linker and attune the rate of
electron transfer from the electrode to the catalyst. This modified
electrodes exhibit stable HER activity over prolonged periods. This
is the first report of direct covalent attachment of an azadithiolate
(ADT) bridged mimic of Fe-Fe H2ase active site to an electrode.
In nature, H2ases are a class of enzyme that interconverts
13
proton (H+) to H2 efficiently.12,
The electrochemical
investigations of H2ases are generally performed by thin film
voltammetry where the enzymes are attached on the electrode
surfaces and such approach has been proved to be an efficient
technique for investigating the reactivities of these enzymes.14-16
Following the original reports, several groups have demonstrated
the suitability of Fe-Fe H2ase mimics as efficient H2 evolution
reaction (HER) in acidic aqueous medium by physiadsorbing them
17
on electrode surfaces.4,
Unfortunately, this often leads to
excessive catalyst loading, slower electron transfer kinetics
between the electrode and the catalyst and gradual leaching of
the adsorbed catalyst.18 Additionally charged molecules do not
physiadsorb on neutral graphite surfaces well. Thus covalent
attachment, without compromising the catalyst structure, can
help to resolve these problems associated with physiadsorption.
Fig. 1 (left) The active site of Fe−Fe hydrogenase, (right) Crystal
structure of p-alkynylbenzeneazidodithiolate diironhexacarbonyl
Covalent attachment of catalysts to electrode surfaces can be
achieved by Cu (I) catalysed 1,3-cycloaddition of azides to
terminal alkyne, a reaction popularly referred as the ‘click’
complex (
A
).
Complex
B
is synthesized by slight modification of procedure
reported by Sun et. al.24 as shown in Scheme 1. Condensation of
dilithium salt of disulphidodiironhexacarbonyl precursor with
N,N-bis(chloromethyl)-4-iodoaniline in tetrahydrofuran yields p-
Department of Inorganic Chemistry, Indian Association for the Cultivation of
Science, 2A&2B Raja SC Mullick Road, Kolkata, India 700032
Electronic Supplementary Information (ESI) available: X-Ray structure, FTIR, ESI MS,
1H NMR and additional electrocatalytic data]. See DOI: 10.1039/x0xx00000x
iodobenzeneazaidodithiolate diironhexacarbonyl complex (B
).27
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 1
Please do not adjust margins

Please do not adjust margins
ChemComm
Page 2 of 4
COMMUNICATION
Journal Name
B (scheme 1) with modified rGOs surface (Hyd-ITO-rGO construct) following the
Palladium catalysed Sonogashira coupling of
trimethylsilylacetylene
gives
p-trimethylsilylacetyleno conditions mentioned above. This HydD-IOTIO: 1-0rG.10O3V9ic/eCwo7nACrstCticr0lue4cO2tn8l1inGies
benzeneazidodithiolate diironhexacarbonyl complex (C) with high characterized by FTIR and X-ray photoelectron spectroscopy
yields.28 The deprotection of the trimethylsilyl group could not be (XPS). The CO vibrations in the IR data at 2084, 2031, 2001, 1990
carried out following the standard literature protocol (potassium and 1963 cm-1 indicates an complex
A and the absence of azide
fluoride and sodium hydroxide) as it resulted in formation of vibration at 2098 cm-1 (present in the ITO-modified rGOs) (Fig. 2
unknown degraded products. The deprotection was finally carried suggest successful 1,3 cycloaddition of complex to the ITO-
out by treating complex with K2CO3 in dry MeOH to afford p- modified rGOs. XPS is a convenient tool to establish the
alkynylbenzeneazadithiolate diironhexacarbonyl complex (A) that immobilization of complex ( ) as binding energies are not only
bears a terminal alkyne group (Scheme 1). Suitable crystal for XRD specific to element but also sensitive to its chemical environment
of the complex was grown by slow evaporation of (charge, oxidation state etc.). The peaks at 711.3 eV and 724.5 eV
a)
A
C
A
A
dichloromethane solution (Fig. 1, right). This reveals the dFe-Fe is correspond to the 2p1/2 and 2p3/2 ionization of Fe(I) centre and the
2.503 Å and dFe-S is 2.208-2.276 Å. These values are consistent peak at 162.4 eV correspond the ionization of 2p of thiolate
with previous reports on similar complexes. The FTIR data of the sulphur. Peaks at 399.8 eV and 402.1 eV represent N1s ionization
complex
A in CH3CN solution shows the carbonyl stretching of the triazole nitrogens and the tertiary nitrogen, respectively. A
frequencies at 2076, 2032, 1998 cm-1. The additional peak at 2298 weak peak at 404.1 eV indicates the presence of some residual
cm-1 represents the C≡CH stretching frequency of the alkyne azides nitrogen (Fig. S2).
group in complex
A
(1H NMR of C≡C-H at 3.042 ppm (SI)).
The CV of the Hyd-ITO-rGO construct showed two reduction
waves at 450 mV and -30 mV and two oxidation waves at 380 mV
I
I
and 95 mV vs Ag/AgCl (Fig. 2b). The scan rate dependence of the
.
e v
q
CV current (Fig. S3a) shows that with the increasing of the scan
rate the splitting between two waves increase. The current vs
scan rate gives a linear curve (Fig. S3b) which confirms the catalyst
is attached on the surface not in solution. Unfortunately these
modified rGO surfaces are not amenable to prolonged electrolysis
under acidic aqueous conditions (Fig. S10). Thus the Hyd-EPG
construct which is stable is used for electrocatalytic HER
investigations.
N
4
(
)
N
Li
S
Li
S
OC
CO
S
e
S
Cl Cl
OC
CO
e
F
e
F
e
F
u er
r
F
CO
CO
OC
OC
THF
S p d y
CO
CO
OC
OC
-
15 o
C
B
,
l
C
2
u
I
C
Pd PPh
(
)
2
3
H
TM
S
r
t
D y E 3N
O
.
a m
t
o
,
,
r
h
N2
60 C 3
Cl
4
O
H
O
H
O
O
Cl
4
.
H
oc
e u v
1
q i
C
l
TMS
B
O
r
(
)
2
ase
,
O
t
N b
3
D y THF 4 h
D y THF
rr overn
E
r
(
)
O
t
S i
t
ig
h
r
N
HN
N
NH2
HN
O
O
D
E
.
.
e v
S
K2CO3 1 5
q
( )
S
S
e
S
OC
CO
OC
CO
.
a
e u v
q i
r
e
F
e
N N3
,
3
r
e
F
e
F
(
)
C
D y M OH
F
CO
OC
OC
,
CO
CO
80 0
OC
OC
DMF 5 h
CO
A
C
O
O
O
O
N3
4
N3
4
Scheme
1
Scheme for single synthesis of complex p-
O
N3
4
O
-
alkynylbenzeneazadithiolate diironhexacarbonyl complex (
A).
er
u
n r
e
t t
yl
i i
F H
C 3COO
t
t
t
B
r
,
,
rr
t
S
i
r
D y A
C
N
O
O
D
M
C
2 h
81.5
170
120
70
0 0
C
Hyd-ITO-rGO
construct
ITO-modified
rGO
HN
NH2
N2
81
80.5
80
F
H
G
Scheme 2 Schematic diagram for the synthesis of the linkers with
azide and amine at the terminal.
20
OC
79.5
79
CO
CO
OC
F
e
F
CO
OC
-30
-80
e
OC
OC
b
a
e
F
S
S
S
e
F
CO
CO
S
78.5
1800
OC
OC
1900
2000
2100
2200
N
0.4
-0.1
V (vs Ag/AgCl)
-0.6
-1.1
N
Wavenumber (cm-1
)
Fig. 2 (a) Overlay of the ATR-IR data of GO (in green), reduced GO
N
N
N
N
N3
N
N
modified with azide terminated amine linker (in sky blue) and
N3
N3
Hyd-ITO-rGO construct (in red). The solution IR data of complex
A
is shown in blue. (
b
) Cyclic voltammogram of Hyd-ITO-rGO
O
O
O
O
O
O
O
O
O
O
construct in pH7 phosphate buffer (scan rate 100 mV/s).
+
u
C
I
N2
( )
Using a benzyl azide, it was found that complex underwent
A
EPG
EPG
EPG
:
:
)
THF H O 1 1
(
2
1,3-dipolar Huisgen addition in THF/H2O (1:1) solvent mixture in
the presence of Cu(I) catalyst in 6 hours. The product formation
was confirmed by 1H NMR and mass spectra (Scheme S1). An Scheme 3 Schematic presentation of covalent attachment for Fe-
azide terminated alkyl amine linker4 is refluxed in CH3CN along Fe H2ase model complex (
with GOs followed by reduction with aqueous NH3 gives the
A) on the modified EPG.
desired azide terminated rGOs. This modified rGOs was then Edge Plane Graphite (EPG) electrode surfaces were functionalized
deposited on ITO surfaces and complex
A
is clicked to this ITO- with complex
A
as well. The original procedure for EPG
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 3 of 4
ChemComm
Please do not adjust margins
Journal Name
COMMUNICATION
modifications developed by Saveant et. al. is implemented here green line). As the acid concentration is increased, the catalytic
View Article Online
with some modifications to construct the azide terminated current density increases and the onset shifts to more positive
DOI: 10.1039/C7CC04281G
modified EPG29, 30 (Fig. S1). The azide terminated aromatic amine potential (Fig. 4
c
). These results are consistent with our previous
similar type hydrogenase mimic was
linkers are synthesized as shown in Scheme 2 and experimental reports, where
a
details are provided in SI. The modified EPG electrode with a physiadsorbed on EPG electrodes.4 This large catalytic response is
phenylene layer bearing aliphatic azide group (Scheme 3) is stable confirmed to be due to HER in situ RRDE where a Pt ring encircles
over a wide range of potential even under strong acidic conditions the EPG disk and is held at a constant potential (0.9 V) to re-
where these H2ase mimic are known to work.9 This procedure oxidize the H2 produced to H+.4 A constant rotation speed of 300
ensures the grafting of a maximum amount of azide moieties rpm is maintained to generate the hydrodynamic force due to
without totally passivating the surface.
Tethering of the complex on the modified EPG surface (Hyd- ring where it is detected. The blue line is (Fig. 4
EPG construct) was further achieved by following the same catalytic H2 production on Hyd-EPG construct and the red line
protocol as described for the Hyd-ITO-rGO construct (Scheme 3). (Fig. 4 ) indicates the oxidation of H2 on the Pt ring establishing
The XPS data obtained (Fig. 3) on the resultant electrode confirm H+ reduction at dilute acid concentrations. The H2 generation is
the covalent attachment of complex on the modified surface. further confirmed by Gas Chromatography (GC).
which the hydrogen generated at the disk is diffused out to the Pt
A
a
) indicates the
a
A
The two sharp peaks centred at 710.9 and 724.5 eV correspond
to the ionization of the 2p1/2 and 2p3/2 levels of the Fe (I) centre
12
25
15
5
a
Hyd-EPG construct
Ring Current (X200)
Modified EPG
a
b
respectively (Fig. 3
a
). The peak centred at 162.5 eV represent the
). A broad
8
ionization of 2p orbital of the thiolate sulphurs (Fig. 3
b
peak centred at 399.4 eV and a shoulder at 402.1 eV indicates the
ionization of 1s orbital of the triazole nitrogen atoms and tertiary
4
-5
amine nitrogen atoms, respectively (Fig. 3c). The data does not
0.6
0.4
0.2
0
0
show any N1s ionization at ~ 404 eV suggesting absence of free
azides upon completion of the click reaction. The ratio of area
under the peaks for the triazole N1s and tertiary N1s is ~3:1,
consistent with the stoichiometry of Hyd-EPG construct.
-15
-25
-4
0
-0.3 -0.6 -0.9 -1.2
E (V vs Ag/AgCl)
E (V vs Ag/AgCl)
12
10
8
Observed
100
80
60
40
20
0
750
0.02 N
a
b
8000
6000
4000
2000
0
Sulphur (2p)
Fit
c
d
c
0.04 N
Iron-2p
600
450
300
150
0
0.06 N
0.08 N
0.1 N
0.12 N
0.14 N
0.16 N
0.18 N
6
4
2
0
705 710 715 720 725 730
Binding Energy(eV)
159.5 161.5 163.5 165.5
Binding Energy(eV)
0
-0.2 -0.4 -0.6 -0.8 -1
E (V vs Ag/AgCl)
0
5
10
15
Time(x103 s)
Observed
N-1s(triazole)
N-1s(tertiary)
Fit
1400
c
6
1200
1000
800
600
400
200
0
Complex A physiadsorbed
on EPG
Hyd-EPG Construct
4
2
0
e
392
397
402
407
Binding Energy(eV)
-0.1
-0.4
-0.7
-1
E (V vs Ag/AgCl)
Fig. 3 X-ray photoelectron spectra of modified EPG electrode
(Hyd-EPG construct). Fe 2p (
a), S 2p (b), and N 1s (c) are shown
here.
Fig. 4
(a) RRDE data of Hyd-EPG construct (blue line, indicating H2
Cyclic Voltametry (CV) of Hyd-EPG construct yields weak and generation and the corresponding Pt-ring current red line,
broad features. So an estimation of the amount of catalyst is indicating H2 detection); the ring held at a constant potential of
difficult. Ethynyl ferrocene is covalently attached instead of 0.9 V in aqueous 0.1 N H2SO4
complex to the azide modified EPG electrode. The CV data of covalently attached to the electrode in 1 N HClO4 at 100 mV/s
this construct shows the Fc/Fc+ process at 0.36 V vs Ag/AgCl in 1N using Pt as counter and Ag/AgCl (satd. KCl) as reference(
) LSV of
HClO4 (Fig. 4 ). The area under the curve yields a coverage of 1.43 Hyd-EPG construct for electrochemical hydrogen generation with
x1014 molecules/cm2. This is two orders of magnitude higher than increasing acid concentration(
Controlled potential bulk
the value obtained using physiadsorbtion and clearly electrolysis at −0.9 V vs Ag/AgCl in aqueous 0.20 N H2SO4 (e) LSV
(b) CV of ethynyl ferrocene
A
c
b
d
)
demonstrates the advantage of covalent attachment over of Hyd-EPG construct(blue) and complex
A physiadsorbed on EPG.
physiadsorbtion.4
The electrocatalytic hydrogen production by the Hyd-EPG
construct is investigated in degassed dilute H2SO4 solution using 0.9 V shows steady consumption of charge at a constant rate
a rotating ring disc electrochemistry (RRDE) setup (Fig. 4 ). The indicating stability of the covalently attached catalyst under long
polarisation curve, when swept from positive to negative term electrocatalytic conditions (Fig. 4 ). The total charge
Bulk electrolysis of the Hyd-EPG construct in 0.20 N H2SO4 at -
a
d
potentials, shows a large catalytic current (Icat) with onset dissipated during the process is 7.67 C over 1200 s and the
potential at -0.72 V vs Ag/AgCl (the modified EPG electrode only, amount of hydrogen gas collected is 0.8 mL through vertical
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

Please do not adjust margins
ChemComm
Page 4 of 4
COMMUNICATION
Journal Name
displacement of water in an inverted burette. The Faradaic yield
(FY) is thus calculated to be 90.7%. The head space gas was
analysed in GC further confirming hydrogen production (Fig. S4).
The advantage of covalent attachment is clear when the HER
International Journal of Hydrogen Energy, 2010, 35, 10790-
View Article Online
10796.
DOI: 10.1039/C7CC04281G
10.
E. S. Andreiadis, P.-A. Jacques, P. D. Tran, A. Leyris, M.
Chavarot-Kerlidou, B. Jousselme, M. Matheron, J. Pécaut,
S. Palacin, M. Fontecave and V. Artero, Nat Chem, 2013, 5,
48-53.
C. Caix, S. Chardon-Noblat, A. Deronzier and R. Ziessel,
Journal of Electroanalytical Chemistry, 1996, 403, 189-202.
J. C. Fontecilla-Camps, A. Volbeda, C. Cavazza and Y.
Nicolet, Chemical Reviews, 2007, 107, 5411-5411.
A. Volbeda, Y. Montet, X. Vernède, E. C. Hatchikian and J.
C. Fontecilla-Camps, International Journal of Hydrogen
Energy, 2002, 27, 1449-1461.
F. A. Armstrong, N. A. Belsey, J. A. Cracknell, G. Goldet, A.
Parkin, E. Reisner, K. A. Vincent and A. F. Wait, Chemical
Society Reviews, 2009, 38, 36-51.
K. A. Vincent, A. Parkin and F. A. Armstrong, Chem. Rev.,
2007, 107, 4366-4413.
currents for the Hyd-EPG construct (Fig. 4
e
blue) is compared to
that of complex physiadsorbed (Fig. 4
A
e, purple) on the EPG
electrodes. The substantially enhanced HER current in the former
is due to higher coverage attained due to covalent modification.
11.
12.
13.
Conclusions
In conclusion a novel Fe-Fe H2ase model having an ADT bridge
and a terminal alkyne is synthesized and attached to graphite
electrode via an azide group bearing linker grafted to the
graphite electrode. The strategy for covalent attachment
developed is modular and amenable to structural modification
of the linker as well as the complex. Using this strategy complex
14.
15.
16.
A
is attached to rGO as well as EPG surfaces. The EPG electrode
bearing covalently attached Fe-Fe H2ase model is found to
retain it’s HER activity and stable over several hours of
electrolysis and no leaching of the catalyst is observed. The
covalent attachment offers two orders of magnitude greater
catalyst coverage without compromising the inherent catalytic
properties of the catalyst.
C. Baffert, K. Sybirna, P. Ezanno, T. Lautier, V. Hajj, I.
Meynial-Salles, P. Soucaille, H. Bottin and C. Léger,
Analytical Chemistry, 2012, 84, 7999-8005.
B. Mondal, K. Sengupta, A. Rana, A. Mahammed, M.
Botoshansky, S. G. Dey, Z. Gross and A. Dey, Inorganic
Chemistry, 2013, 52, 3381-3387.
17.
18.
19.
20.
21.
22.
23.
I. Sadaba, M. Lopez Granados, A. Riisager and E. Taarning,
Green Chemistry, 2015, 17, 4133-4145.
H. C. Kolb, M. G. Finn and K. B. Sharpless, Angew. Chem.
Int. Ed., 2001, 40, 2004-2021.
S. Samanta, P. K. Das, S. Chatterjee, K. Sengupta, B. Mondal
and A. Dey, Inorganic Chemistry, 2013, 52, 12963-12971.
A. Devadoss and C. E. D. Chidsey, Journal of the American
Chemical Society, 2007, 129, 5370-5371.
G. Clave and S. Campidelli, Chemical Science, 2011, 2, 1887-
1896.
J. P. Collman, N. K. Devaraj, R. A. Decréau, Y. Yang, Y.-L. Yan,
W. Ebina, T. A. Eberspacher and C. E. D. Chidsey, Science,
2007, 315, 1565-1568.
A. Le Goff, V. Artero, B. Jousselme, P. D. Tran, N. Guillet, R.
Métayé, A. Fihri, S. Palacin and M. Fontecave, Science,
2009, 326, 1384-1387.
F. Wang, W.-J. Liang, J.-X. Jian, C.-B. Li, B. Chen, C.-H. Tung
and L.-Z. Wu, Angewandte Chemie International Edition,
2013, 52, 8134-8138.
G. Berggren, A. Adamska, C. Lambertz, T. R. Simmons, J.
Esselborn, M. Atta, S. Gambarelli, J. M. Mouesca, E.
Reijerse, W. Lubitz, T. Happe, V. Artero and M. Fontecave,
Nature, 2013, 499, 66-69.
S. Ott, M. Kritikos, B. Åkermark, L. Sun and R. Lomoth,
Angewandte Chemie, 2004, 116, 1024-1027.
S. Ott, M. Borgström, M. Kritikos, R. Lomoth, J. Bergquist,
B. Åkermark, L. Hammarström and L. Sun, Inorganic
Chemistry, 2004, 43, 4683-4692.
M. Delamar, R. Hitmi, J. Pinson and J. M. Saveant, J. Am.
Chem. Soc., 1992, 114, 5883-5884.
P. Allongue, M. Delamar, B. Desbat, O. Fagebaume, R.
Hitmi, J. Pinson and J.-M. Savéant, J. Am. Chem. Soc., 1997,
119, 201-207.
Acknowledgements
The research was funded by MNRE 103/180/2010-NT. E.A.
acknowledges CSIR-JRF, S.D. acknowledges IACS Institute Fellow
Scheme and B.M. acknowledges CSIR-SPM-SRF. The IACS XPS
facility funded by DST unit of Nano-science is gratefully
acknowledged. We greatly acknowledge Mr. Diptiman Dinda for
providing us GO and also for his help to synthesize the rGO.
Notes
All the potentials mentioned in the manuscript are reported with
respect to Ag/AgCl (sat. KCl) electrode. The Authors declares no
conflict of interest. The modified complex A after clicking on to
surface is denoted as “Hyd”.
24.
25.
26.
References
1.
2.
3.
4.
5.
6.
7.
A. J. Bard and M. A. Fox, Accounts of Chemical Research,
1995, 28, 141-145.
M. Graetzel, Accounts of Chemical Research, 1981, 14, 376-
384.
N. Armaroli and V. Balzani, Angewandte Chemie
International Edition, 2007, 46, 52-66.
S. Dey, A. Rana, S. G. Dey and A. Dey, ACS Catal., 2013, 3,
429-436.
I. J. McPherson and K. A. Vincent, Journal of the Brazilian
Chemical Society, 2014, 25, 427-441.
V. S. Thoi, Y. Sun, J. R. Long and C. J. Chang, Chem. Soc. Rev.,
2013, 42, 2388-2400.
V. Vijaikanth, J.-F. Capon, F. Gloaguen, F. Y. Pétillon, P.
Schollhammer and J. Talarmin, Journal of Organometallic
Chemistry, 2007, 692, 4177-4181.
27.
28.
29.
30.
8.
9.
C. M. Thomas, O. Rüdiger, T. Liu, C. E. Carson, M. B. Hall
and M. Y. Darensbourg, Organometallics, 2007, 26, 3976-
3984.
A. Le Goff, V. Artero, R. Metayé, F. Moggia, B. Jousselme,
M. Razavet, P. D. Tran, S. Palacin and M. Fontecave,
4 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins