Iron and Cobalt Corroles in Solution and on Carbon Nanotubes as Molecular Photocatalysts for Hydrogen Production by Water Reduction

Article abstract of DOI:10.1002/cctc.201700349

Herein, we report the use of cobalt and iron corrole complexes as catalysts of H₂O reduction to generate H₂. Electro- and photocatalysis has been used in the case of dissolved corroles for water reduction with inspiring results. Carb

Full text of DOI:10.1002/cctc.201700349

Accepted Article
Title: Iron and cobalt corroles in solution and on carbon nanotubes
as molecular photocatalysts for hydrogen production by water
reduction
Authors: Miguel A. Morales Vásquez, Mariana Hamer, Nicolas I.
Neuman, Alvaro Y. Tesio, Andrés Hunt, Horacio Bogo,
Ernesto J. Calvo, and Fabio Doctorovich
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: ChemCatChem 10.1002/cctc.201700349
Link to VoR: http://dx.doi.org/10.1002/cctc.201700349
A Journal of
www.chemcatchem.org

10.1002/cctc.201700349
ChemCatChem
FULL PAPER
Iron and cobalt corroles in solution and on carbon nanotubes as
molecular photocatalysts for hydrogen production by water
reduction
Miguel A. Morales Vásquez[a]§, Mariana Hamer[b]§, Nicolás I. Neuman[a][c], Alvaro Y. Tesio[a], Andrés
Hunt[a], Horacio Bogo[a], Ernesto J. Calvo[a] and Fabio Doctorovich[a]*
[a] INQUIMAE; Departamento de Química Inorgánica, Analítica y Química Física; CONICET; Facultad de Ciencias Exactas y
Naturales; Universidad de Buenos Aires. Ciudad Universitaria; Pabellón II; Buenos Aires (C1428EHA); Argentina.
[b] Instituto de Nanosistemas, Universidad Nacional de San Martin; CONICET, Buenos Aires (B1650); Argentina.
[c]
Departamento de Física, FBCB-UNL, CONICET, Facultad de Bioquímica y Ciencias Biológicas, Ciudad Universitaria, Ruta N 168
S/N, S3000ZAA Santa Fe, Argentina
§ These authors participated equally in the development of this work.
*e-mail: doctorovich@qi.fcen.uba.ar; Fax: 54-11-4576-3341
RECEIVED DATE
Abstract:
Metallocorroles and metalloporphyrins have shown to be
Here we report the use of cobalt and iron corrole complexes as
promising potential catalysts for H2 evolution in photocatalytic
catalysts of H2O reduction to generate H2. Electro and photocatalysis
systems, in which a sensitizer mediates electron transfer
has been used in the case of dissolved corroles for water reduction
from a sacrificial donor to the catalyst, which in turn reduces
with inspiring results. Carbon nanotubes doped with corroles were
used as photo-electrochemical catalysts allowing getting very low H+ to H2.[1] Corroles are 18- electron tetrapyrrolic
macrocycles containing a direct pyrrole–pyrrole bond,[2] and
overpotential values and increased hydrogen production, achieving
incredibly high turnover numbers and turnover frequencies of ca. 107
and 105, respectively. Through this last process we were able to
porphyrins.[3] Corroles have several interesting properties,
obtain 1mmol of H2 by using minuscule amounts of catalyst, in the
among which is their trianionic nature upon deprotonation,
order of pictograms. The reactions can be carried out in water,
have a smaller cavity and lower symmetry-C2v compared to
which tend to stabilize transition metals in higher oxidation
without the need of organic solvents. Remarkably, the
[4–6]
states compared with porphyrins.
They also have a
photoelectrochemical catalytic efficiency was increased by five orders
of magnitude when adsorbing the molecular catalysts onto carbon
nanotubes.
higher N-H acidity and high fluorescence levels.[7–10]
Efficient synthetic methods developed by Gross et
al.[11,12], Paolesse et al.[13] and Gryko et al.[14,15] opened the
doors for the progress of many new studies in corrole (photo
and electro-) chemistry, spectroscopy and applications. Later
Spiro et al.[16] have shown CoI porphyrin electrocatalyzed
formation of H2 in solution, and more recently we have
Introduction
Replacement of fossil fuels with renewable energy
sources, such as solar or wind, requires energy storage for
the periods were these are inactive.[1] Hydrogen obtained
from water is a candidate of great interest to replace these
other sources of energy as it is a clean, cheap and
renewable fuel.[2] Many techniques for H2 production from
natural gasoline, methanol, gas, biomass, and other non-
renewable materials have been studied,[1] but the efficient
generation from water still remains the crux of a hydrogen-
based economy.[3]
reported hydrogen evolution using
a cobalt porphyrin
anchored on a gold electrode with a TON≈106.[17]
Due to the trianionic nature of free base corroles, the
metal centers of corroles can reach oxidized states more
easily than porphyrins. Therefore, the photoreduced CoI
corroles should be more reactive towards H+ reduction. This
behavior was observed by Solomon et. al,[18] who studied the
differences in energy in the oxidation state between corroles
and porphyrins, and their interactions with metals. They
1
This article is protected by copyright. All rights reserved.

10.1002/cctc.201700349
ChemCatChem
FULL PAPER
showed that there are more accessible states in the corrole
nanomaterials in order to improve the reduction of
[30]
which allows more accessible reduction of the metal center.
oxygen[27,29,30], reduction of nitric oxide
water.[19,31]
and oxidation of
Hydrogen obtained in photocatalytic systems is
produced by reduction of the catalyst using electrons
obtained from a sacrificial donor; electron transfer occurs by
way of a photoinduced sensitizer, which is regenerated by
the sacrificial donor.[4] However; photocatalysis has not been
used in the case of corroles for water reduction.
In this work, we describe photocatalytic H2 evolution
experiments performed using cobalt and iron corroles
(Scheme 1A) and discuss the relation between the catalyst
efficiencies and their electrochemical and physicochemical
properties. Furthermore, we describe the synthesis,
characterization and photoreactivity of carbon nanotubes
(MWNT) doped with Co(III)-Corrole (Scheme 1B) towards
water reduction in aqueous solution.
Results and Discussion
-
Study of hydrogen production using corroles as
photocatalysts.
Free base corrole ligands were synthesized and in a
second step were metallated with cobalt and iron. The main
spectroscopic and electrochemical parameters of the
obtained metallocomplexes are summarized in Table S1.
Experiments to determine the performance and the
catalytic parameters for H2 production for these organic
catalysts in solution were performed using the setups shown
in the Supporting Information (Figures S1-S4) using TEA
(triethylamine) as sacrificial donor and TP (terphenyl) as a
sensitizer.[32]
In 2002 Gross et al.[33], reported a similar set up for
catalytic reduction of CO2, and described the following
mechanism:
Scheme 1. (A) Synthesized corroles. (B) Schematic representation
of the absorbed metallocorrole on SWNT.
퐓퐏 퐡 퐯 퐓퐏∗
(1)
퐓퐏∗ + 퐄퐭ퟑ퐍 퐓퐏•− + 퐄퐭ퟑ퐍•+
(2)
On the other hand, fundamental progress has been
made in developing novel material structures for gaining this
goal. Nanomaterial composites and structures, including
The metal center is readily reduced by the radical TP•-, which
has a very negative reduction potential (-2.45 V vs SCE in
dimethylamine).[34]
inorganic,
materials,[19,20] have been explored to meet specific
requirements such as light-absorbing wavelength
molecular
and
hybrid
organic/inorganic
퐈퐈퐈
퐈퐈
−
a
퐓퐏•− + 퐌 퐂퐨퐫 퐓퐏 + 퐌 퐂퐨퐫
(3)
(4)
modification,[21,22] photoinduced charge separation[23,24] and a
faster water-splitting reaction.[25] A great number of catalysts
systems for energy storage and conversion has been based
on carbon nanotubes (CNT) as they have the capability to
contribute not only in charge injection and extraction, but also
they increase the direct flow of photo-generated electrons.[26–
퐈퐈
−
퐈
ퟐ−
퐓퐏•− + 퐌 퐂퐨퐫
퐓퐏 + 퐌 퐂퐨퐫
Et3N•+ reacts with a molecule of TEA to form a carbon
centered radical (E1/2= -1.12 V vs. SCE in MeCN), which
reduces the metal center [MIII(Cor)], but cannot reduce
[MII(Cor)]-. [35]
28]
Recently, CNT were used in the synthesis of different
퐄퐭ퟑ퐍•+ + 퐄퐭ퟑ퐍 퐄퐭ퟑ퐍퐇+ + 퐄퐭ퟐ퐍퐂퐇퐂퐇ퟑ
(5)
2
This article is protected by copyright. All rights reserved.

10.1002/cctc.201700349
ChemCatChem
FULL PAPER
퐈퐈퐈
+
퐈퐈
퐄퐭ퟐ퐍퐂퐇퐂퐇ퟑ + 퐌 퐂퐨퐫 퐄퐭ퟐ퐍 + 퐂퐇퐂퐇ퟑ + 퐌 퐂퐨퐫 −(6)
depicted in Figure S1. Figure S7 shows the gas production
for two catalysts, NO2-Cor-Co and Cl2-Cor-Co, after the first
addition of water. Since free radicals are formed, it is also
possible that these free radicals intervene in chain reactions
which regenerate the radicales and produce H2. The electron
donor is triethylamine, as described above. Regarding the
catalyst, It is thought that the Soret band disappears due to
unwanted hydrogenation of the macrocycle.
The photochemical reduction causes the production of
acid (as shown in reaction 7), which can protonate [MI(Cor)]2-
and subsequently form the respective metal hydride, which
can be protonated to form H2, or hydrogenate the macrocycle
(as seen with porphyrins).[32,35,36]
퐈
퐈퐈
퐌 퐂퐨퐫 ퟐ− + 퐄퐭ퟑ퐍퐇+ 퐇 퐌 퐂퐨퐫 − + 퐄퐭ퟑ퐍
(7)
(8)
퐈퐈
퐈퐈퐈
퐇 퐌 퐂퐨퐫 − + 퐄퐭ퟑ퐍퐇+ 퐌 퐂퐨퐫 + 퐇ퟐ + 퐄퐭ퟑ퐍
The addition of TEA did not result in a significant
change in the UV-Vis spectra. However TEA may replace the
[32,36,37]
axial ligand and also reduce the metal center.
It is
important to emphasize that no hydrogen is obtained under
the present reaction conditions from TEA if the photocatalysis
is carried out in the absence of water.
Hydrogen production was confirmed by detecting the
produced gas while carrying out photocatalysis experiments,
as the reaction system was connected to a DEMS (Figure
S4). Figure S5(A) and (B) show the identification of the gas
generated during the photocatalysis: hydrogen (m/q =
2);argon (m/q = 40) is used to obtain the inert atmosphere.
Furthermore, while following the ionic current (m/q=2) in real
time, the immediate intense bubbling (Figure S6 and
multimedia) and formation of H2 after the addition of H2O to
the catalyst/TP/TEA mixture can be observed.
Figure 1. Time dependent traces taken from the UV-Vis spectrum
using NO2-Cor-Co as photocatalyst. Green: before irradiation
(Co(III)). Blue: during photocatalysis (Co(I)). Orange: degraded
catalyst.
The different metallocorroles show similar values for
TON, TOF and amount of H2 generated (Table 1). This fact
can be explained by the use of TP as a sensitizer, which
having a very negative reduction potential is able to reduce
all studied metallocorroles at similar rates, regardless of their
individual redox properties. Furthermore, the TOF values are
similar for most studied cobalt corroles, which suggests that
the observed TOF is not a measure of the intrinsic efficiency
of the metallocorrole, but a global TOF of the whole electron
donor-photosensitizer-catalyst assembly. Therefore, we
conducted several experiments where no TP was used in
order to observe differences in the production of H2
depending on the electron donating or withdrawing
substituents. Some of the catalytic parameters obtained in
the absence of TP are shown in Figure 2 and Table 2. The
presence of an electron-attracting group such as –NO2
increases the performance of the catalyst.
Table 1 summarizes the results for H2 generation for all
the catalysts tested. The amount of H2 produced by cobalt
and iron metallocorroles is similar, with the latter being a little
less efficient.
Table 1. Results of hydrogen production. [a]
Catalyst
NO2-Cor-Co
TP-Cor-Co
Cl2-Cor-Co
NO2-Cor-Fe
TP-Cor-Fe
Cl2-Cor-Fe
TON
TOF (min-1)
3.76±0.12
1.79±0.15
3.30±0.12
1.9±0.8
H2 (mol) ×10-4
8.5±0.9
113.3±1.1
80.4±0.9
83.1±1.1
86.3±1.2
80.0±1.1
83.3±1.0
6.0±1.1
6.2±0.9
6.5±0.8
6.0±1.2
1.8±0.6
3.7±0.9
6.2±0.7
[a] All experiments were performed in triplicate. The reactions were carried
out at r.t and with continuous UV irradiation. 7.5×10-6 mol of catalyst in
the presence of 3 mM of TP and 5% v/v of TEA were dissolved in 10 mL
of 1,4-dioxane.
Figure 1 shows the UV-Vis spectrum changes for NO2-
Cor-Co while irradiating. After irradiating for 15 minutes the
reduction of the metal center to Co(I) is observed (blue).
Then, following the addition of water, the catalyst returns to
its oxidized state (green). However, after the second addition
of water the metallocorrole was degraded (orange). The
volume of gas generated was measured by using the setup
3
This article is protected by copyright. All rights reserved.

10.1002/cctc.201700349
ChemCatChem
FULL PAPER
A proposed mechanism for the catalytic reduction of
water to hydrogen is presented in Scheme 2 which shows the
formation of a hydride cobalt adduct which can be described
as Co(II)-H or Co(III)-H-). The so formed cobalt hydride can be
attacked by a proton to produce H2 and re-form the catalyst
[Co-Cor(III)] in order to restart the catalytic cycle. This
pathway is postulated as the main one, the difference being
that when working with the sensitizer (TP), instead of Co(II)
Co(I) is obtained, as described above (see equations 1-8).
By irradiation using a UV lamp, the reduced catalysts
are obtained by electron donation from TEA; in some cases,
these processes are MIIICorr→MIICorr, and in others
MIICorr→MICorr. If MII-Cor is the main product, then the
hydride can be formulated as H•-CoIII-Cor, which could
dimerize and/or liberate H• to produce H2.
Figure 2. Evolution of gas formed during catalysis using NO2-Cor-Co
catalyst in the presence and absence of TP and successive 100 μL
H2O additions. Catalyst amount: 7.5x10-6 mol Temperature: 25 ºC.
TEA: 5% v/v; TP: 3 mM
Table 2. Results of hydrogen production in the absence of TP. [a]
This mechanism was previously proposed by Gross and
coworkers, based on theoretical calculations. [39]
Catalyst
TON
TOF (min-1)
H2 (mol)×10-4
NO2-Cor-Co
TP-Cor-Co
Cl2-Cor-Co
76.3±1.2
30.0±1.1
27.7±1.0
1.3±0.4
0.5±0.1
0.5±0.2
5.7±0.9
2.3±0.8
2.1±0.9
[a] All experiments were performed in triplicate. The reactions were carried
out at r.t and with continuous UV irradiation. 7.5×10-6 mol of catalyst in
the presence of 3 mM of TP and 5% v/v of TEA were dissolved in 10 mL
of 1,4-dioxane.
There appears to be
a correlation between the
absorptivities of the LMCT bands in the 200-300 nm range
for all cobalt corroles and the efficiency of H2 production in
the absence of a second photosensitizer (TP). Since the
lamp used in the experiments has excitation lines at 184 and
253 nm and the line at 253 nm is absorbed by the LMCT
band [38] (Table S1) giving raise to the excited state of the
porphyrin/corrole, prone to reduction of the metal center. The
absorptivities of the LMCT bands diminish in the following
order: NO2- (28.8, 267) > Cl2- (15.7, 291) > TP (12.2, 264).
Similarly, the TON and TOF values of hydrogen production
catalyzed by the cobalt corroles descend in the order (TON,
TOF in min-1): -NO2 (76, 1.3) > TP- (30, 0.5) > -Cl2 (28, 0.5).
It would seem that the degree to which each cobalt corrole is
able to absorb radiation from the lamp is correlated with its
H2 production capacity, but the differences in TOF and TON
are not large.
Scheme 2. Proposed mechanism for the photocatalytic production of
H2 from water.
The relatively low TON values observed are probably
due to bleaching of the catalyst by the UV light and/or
hydrogenation of the macrocycle.
-
Co(III)-p-nitro phenyl corrole adsorbed on carbon
nanotubes
We have proved that it is possible to obtain hydrogen
from water by reducing metallocorrole catalysts by UV
irradiation and that in the presence and absence of TP, NO2-
Cor-Co was the most effective catalyst. Therefore, we
decided to adsorbe the Co(III)-p-nitro phenyl corrole on
carbon nanotubes and study the catalytic performance of this
nanocomposite.
It can be concluded that the substituents on the
aromatic rings do not exert a major role on the efficiency of
the catalyst, except in the modification of the absorptivities of
the LMCT bands. This is possibly due to the fact that either
with or without TP, the energy of the Hg lamp is so high that
all studied systems are effectively reduced to CoI or FeI.
The MWNT were activated[27] and modified with Co(III)-p-
nitro phenyl corrole (MWNT/NO2-Cor-Co). The morphology
4
This article is protected by copyright. All rights reserved.

10.1002/cctc.201700349
ChemCatChem
FULL PAPER
and structure of the prepared nanocomposite were analyzed
by TEM and SEM (Figure 3, S8 and S9).[40] The general
aspect of the uncoated and the functionalized nanotubes is
similar in terms of diameter and length. However, the
functionalized nanotubes present a thin layer of NO2-Cor-Co,
which is exclusively located around the nanotubes surface
and is corroborated by a more intense contrast in the TEM
images and the different aspect of the nanomaterial on the
SEM micrograph.[27,41] The amount of adsorbed corrole on
the nanotubes was determined to be (0.06 ± 0.02)% of the
total weight of the nanocomposite.
Figure 4. Raman Spectra of MWNT (A), (B) MWNT/NO2-Cor-Co and
(C) Co-corrole (normalized). Black arrows indicate the signals due to
the immobilized corrole.
On the other hand, the characteristic Raman spectrum of
MWNT in the range of 200–1800 cm−1 is dominated by two
peaks: one at 1371 cm−1 and another one at 1577 cm−1,[52–54]
which downshifts (6 cm-1) in the nanocomposite, suggesting
non-covalent strong interactions, such as hydrogen bonds
and - stacking between the corrole ring and MWNT.[55]
The photocatalytic performance of the nanocomposite
was studied by UV-Vis spectroscopy. Figure S11 depicts the
temporary changes of the Soret band while irradiating. These
results also evidenced in the transition CoIIICoIICoI,
proving that there is also a direct effect of the irradiation on
the reduction of the metal center of the corroles present in
the nanocomposites.
Figure 3. TEM image of MWNT/NO2-Cor-Co. The corrole coating
can be observed as a shade when the image is compared with the
TEM image of unmodified MWNTs (Figure S8).
The UV-vis signals of corroles adsorbed on the nanotube
surface are considerably broadened and red-shifted (~12
nm), clearly indicating the formation of conjugated corrole-
MWNT with a strong - interaction (Figure S10).[40,42–44]
Moreover, after sonication, the absorbance spectra of MWNT
solutions show a maximum at 264 nm[45–47] which is also red-
shifted (~30 nm) after the modification. The shift observed is
a direct evidence of the - interaction between the nanotube
sidewall and the corrole ring in the nanocomposite
dispersion.[48] The Resonant Raman (RR) features observed
in the spectra given for NO2-Cor-Co mainly arise from pyrrole
and phenyl units of the macrocycle (Figure 4 and Table
S2).[49–51] It is worth mentioning that in the nanocomposites
some small signals in the low frequency region (380, 990,
1074 and 1234 cm-1) corresponding to the corrole molecule
can be observed.
Hydrogen production by photocatalysis was confirmed by
measuring the gas volume with a burette and also by
quantifying H2 through GC-TCD analysis of the H2 peak
(Table 3). Figure 5 shows the volume of H2 produced vs time
measured by the gas burette using MWNT/NO2-Cor-Co. TON
and TOF values for these experiments are shown in Table 3.
It is worth mentioning that no gas is produced unless water is
added. Experiments were performed with MWNT without
metallocorrole, in which no hydrogen is obtained; this shows
that the MWNT/NO2-Cor-Co catalyst is that it produces
hydrogen in the presence of water.
Table 3. Photocatalytic parameters obtained for hydrogen
production by using MWNT/NO2-Cor-Co.
Exp.
Gas burette
GC-TCD
Solvent
TON×105
TOF (min-1)
×104
dioxane[a]
buffer[b]
dioxane[a]
buffer[b]
5.111.26
7.011.23
4.201.03
7.011.09
0.840.08
1.200.10
0.720.09
1.200.02
[a] All experiments were performed in triplicate. The reactions were carried
out at r.t and with continuous UV irradiation in 1,4-dioxane.
[b] All experiments were performed in triplicate. The reactions were carried
out at r.t and with continuous UV irradiation. 7.5×10-6 mol of catalyst in
buffer formate.
5
This article is protected by copyright. All rights reserved.

10.1002/cctc.201700349
ChemCatChem
FULL PAPER
Considering the above results we proceeded to study
MWNT-NO2-Cor-Co toward H2 production at pH = 3 (formate
buffer). A larger amount of H2 was obtained, since a higher
concentration of H+ is present.[39]
study the photoelectrochemical performance of the
nanocomposite, CVs between -1000 to +200 mV were
recorded while irradiating (Figure 6A). Without irradiation, a
reversible wave at -526 mV vs. NHE of about 3μA was
observed, which probably corresponds to the redox couple
CoIII/CoII. But after 20 min of irradiation, an increase in the
amplitude (8μA) and a shift of the peak to a less negative
reduction potential (-251 mV) was detected. Not only is it
possible to reduce the overpotential by almost 300 mV by
irradiation, also the current -and therefore the reduction rate-
is tripled.
So, photoamperometric measurements were performed
at -251 mV. The response of the current to the addition of
water is shown in Figure 6B. The negative current increases
with the amount of added water, with the consequent
appearance of H2 bubbles. The volume of gas produced was
measured by a gas burette, and 1.2 mmol of H2 were
obtained by adding 27 mmol of water, with TON and TOF
values of (1.0±0.3)×107 and (3.4±0.1)×105, respectively. Id
est, one order of magnitude higher compared to the values
displayed in Table 4. After 30 minutes the catalyst was
degraded.
Figure 5. H2-production using MWNT-NO2-Cor-Co in buffer formate
pH = 3, with the setup shown in Figure S1.
The
catalytic
parameters
obtained
for
the
nanocomposites are several orders of magnitude higher than
those obtained with the corroles in solution. Furthermore, the
TON value is very similar to that obtained electrochemically
with the use of metallocorroles by Gross and collaborators
(>107), although the TOF value is several orders of
magnitude higher in our case (104 versus 10), and the pH
much less acidic (pH = 0.3 vs. pH = 3).[39]
MWNTs are good electron acceptors and act as effective
electron transfer units because of their high electrical
conductivity and high electron storage capacity.[56,57]
Therefore, in the current system the MWNT act as a photo-
activated electron acceptor and electron-storage system that
promotes interfacial electron transfer processes towards the
deposited metallocorroles, increasing enormously the
reduction rate of the metal center.[23,58] Moreover, the
presence of the nanotubes in the nanocomposite can inhibit
the recombination of photo-generated electrons, improving
the photocatalytic activity.[23,59]
The transmission stability of promoted electrons between
the nanotubes and the conduction band is enhanced by the
strong - interaction and intimate contact between the
corrole ring and the surface of the nanotubes, which was
corroborated by UV-Vis and Raman analysis.
The nanocomposites were also studied by CV (Figure
S12), the voltammograms show two irreversible processes,
and a reversible one: an oxidation process (III), due to the
CoIV/CoIII couple and two reduction processes, irreversible I
(MWNT) and reversible II (probably CoIII/CoII), respectively,
indicating the presence of the metallocorrole. In order to
Figure 6. (A) CV vs. NHE, of the MWNT/NO2-Cor-Co (5.8×10-8 M) in
formate buffer, pH = 3, (scan rate = 100 mV/s) while irradiating: 0
min (black), 5 min (green), 15 min (blue), 20 min (red) and 30 min
(pink). Full scan range [-1200 to 1000 mV]. (B) Photoelectrochemical
amperometric measurements at -251 mV vs. NHE with addition of 0,
100, 200, 300, 400 and 500µL of water. Total range 4800 s (see
Figure S13).
6
This article is protected by copyright. All rights reserved.

10.1002/cctc.201700349
ChemCatChem
FULL PAPER
The amount of gas produced by photoelectrocatalysis
increases up to thirty times (Table 4) compared to the
amount obtained by photocatalysis (Table 2). Therefore,
photoelectrochemical catalysis accelerates the flow of
electrons and the catalyst metal center is reduced faster and
easier, obtaining larger amounts of gas at higher rates. It is
worth mentioning that in this experiment an intense bubbling
was observed.
the differences in TON and TOF are not significant for
different substituents on the aromatic rings. Therefore, we
conclude that they do not exert a major role on the efficiency
of the catalyst, although they do affect the reduction potential
of the Co(II)/Co(I) redox couple.
Spectroscopic data suggest that Co(I) and/or Co(II) is
the active form of catalyst that generates hydrogen, which
was also demonstrated by Gross and coworkers.[39] The
difference in catalytic efficiency between cobalt and iron
follows the pattern shown by the ring substituents and is also
small.
Table 4. Catalytic parameters obtained in photoelectrocatalysis and electrocatalysis
experiments. (Figure S14 shows the curve for dioxane experiments)
Exp.
Catalyst
Photoelectrocatalysis
MWNT/NO2-Cor-Co
Electrocatalysis Photocatalysis
[b]
Co-F8
Cobalaximes[c]
CH3CN/H2O
(24:1) v/v
2.15×103
3.6
Solvent
dioxane
buffer
0.5 M H2SO4
Other catalysts that have similar structures with cobalt
as metal center have shown production of hydrogen with a
TON and TOF a little lower and much more severe reaction
conditions than those used in this work.[61]
TON
>>107
10
(8.051.62 )×106
(1.010.33 )×107
TOF (min-1)
Potential
(mV) [a]
(2.6812)×105
(3.350.1)×105
-251
-251
-241
-886
[a] Measured potentials vs. NHE.
[b]Reference [39]
[c]Reference [60]
.
Possibly,
most
metallocorroles
could
show
A proposed mechanism for the photoelectrocatalytic
reduction of water to hydrogen is presented in Scheme 3
which shows the formation of a hydride cobalt adduct which
can be described as Co(II)-H or Co(III)-H-). The formed cobalt
hydride can be attacked by a proton to produce H2 and re-
form the catalyst [Co-Cor(III)] in order to restart the catalytic
cycle.
photocatalytic activity for the production of hydrogen from
water, regardless of the substituents or the metal center.
Although the obtained photocatalytic activity in solution is
relatively low, it can be enormously increased by
immobilizing the catalysts on surfaces. This was shown by
adsorbing Co(III)-p-nitro phenyl corrole on carbon nanotubes
and studying the catalytic performance of this nanocomposite.
The metallocorroles adsorbed on nanotubes showed a
spectacular catalytic response. It is possible to reduce the
overpotential to very low values (-251 mV vs. NHE) with a
huge catalytic efficiency for hydrogen production. It can be
said that the results achieved so far are innovative and
powerful, since through the photoelectrochemical process it
was possible to obtain 1 mmol of H2 by using a minuscule
amount of catalyst, in the order of picograms.
It is important to remember that the best catalyst should
present high TON and TOF values and low over potentials.
So MWNT-NO2-Cor-Co, which is comparable to that
developed by Gross,[39] shows a similar overpotential, similar
TON values, but much higher TOF values. Moreover: our
catalyst works at pH = 3, while Gross´s catalysts was tested
in 0.5 M H2SO4 (pH = 0.3). With the data collected in this
work and other recent publications, we can construct a graph
evaluating the catalytic parameters, shown in Figure 7,
adding the best molecular catalysts that we were able to find
in the literature,[17,39] compared to the one developed in this
work.
Scheme 3. Proposed mechanism for the photoelectrocatalytic
production of H2 from water.
Conclusions
It is possible to obtain hydrogen from water by reducing
metallocorrole catalysts by UV irradiation; in some cases,
MIIICor→MIICor
MIICor→MICor.
processes
occur,
and
in
others,
In the presence and in the absence of TP, NO2-Cor-Co
resulted to be the most efficient catalyst, probably due to the
electron-withdrawing effect of the –NO2 substituent. However,
7
This article is protected by copyright. All rights reserved.

10.1002/cctc.201700349
ChemCatChem
FULL PAPER
voltammetries (CV), the organic solvents used were dichloromethane
(DCM) and acetonitrile (MeCN). Two platinum Pt-wire was used as
reference and counter electrode and a 3 mm glassy carbon disc was
used as a working electrode. N(Bu)4PF6 (0.1M) was used as
supporting electrolyte. The solutions were free of air and
voltammetries were performed under an argon inert atmosphere.
The pseudo-reference potential was calibrated with Fc and then
transformed to E vs. SCE E(SCE) = E(Fc) +320 mV. 1H NMR spectra
were performed on a Bruker AM-500 MHz in deuterated solvents
obtained from Sigma-Aldrich (CDCl3 and Pyridine-d5).
A mercury lamp (Hg) of low pressure was used for irradiation.
This lamp shows intense UV lines at 184 and 253 nm. The lamp was
located at 40 cm (this distance was sufficient to prevent heating of
the solution) of the quartz vessel used for the experiments (a round-
bottomed flask of 25 mL). The volume (mL) of the gas obtained from
photocatalysis was quantified using a gas burette which is depicted
in Figure S1. All volumes reported in this paper were measured at
atmospheric pressure.
Figure 7. Plot of the catalytic parameters obtained from the literature
and from Tables 1. Potential reported vs. NHE. Violet (MWNT/NO2-
Cor-Co), red (CoTPP), orange (NO2-Cor-Co), pink[39]
, ,
black[62]
blue[63] and brown[64]
.
The best catalyst in the plot would be the one located on
the vertex (highest TON and TOF valuest, lowest
overpotential).
Mass spectrometry was accomplished for the detection of the
gas products, using a Pfeiffer vacuum Omnistar GSD 320 gas
analysis system with a quadrupole mass spectrometer QGM 220
(mass range 1−200 amu, PrismaPlus) with ion gastight ion source,
iridium-filament with secondary electron multiplier C-SEM and
Faraday detectors. QUADERA software was used for data
acquisition and control. The setup involves placing the gas analyzer
capillary at one of the outputs of a booth-necked quartz flask
containing solution of the metallocorrole. The output was free to
perform water additions, using a micro syringe, through a septum
closure. The gas detector was connected to the photocatalytic
system as shown in Figure S4.
The immobilization approach without linkers reported in
this work provides a simple and efficient methodology for the
future study of the activity and stability of a variety of
molecular catalysts in aqueous media. Furthermore, the
photoelectrochemical catalytic efficiency increased 5 orders
of magnitude when adsorbing the molecular catalysts onto
carbon nanotubes.
Experimental Section
The UV-visible spectra were obtained using an Agilent 8453
diode array spectrophotometer, with thermostatic bath and quartz
cuvettes of 1 cm optical path. For sensitive measurements, Schlenk
cuvettes and cuvettes with Teflon or silicone septa were used,
allowing the addition of reagents by the use of syringes. In order to
measure the UV-Vis spectra during the photocatalysis, the system
shown in Figure S3 was designed and developed.
-
Chemicals
Triethylamine (TEA), p-terphenyl (TP) and ferrocene (Fc),
substituted
benzaldehydes
(p-nitrobenzaldehyde,
2,6-
dichlorobenzaldehyde and benzaldehyde), pyrrole, were purchased
from Sigma-Aldrich. N(Bu)4PF6 and KNO3 were purchased from
Merck.
Nanotubes size and morphology were verified by TEM. MWNT
and nanocomposites dispersed in acetonitrile were imaged in a TEM
Zeiss EM109T Transmission Electron Microscope after placing drops
of dispersion onto gold grids, 400 mesh (SPI, PA, USA), and
allowing the liquid to dry in air at room temperature. The scanning
electron micrographs were obtained using a Carl Zeiss NTS SUPRA
40 SEM with Field Emission Gun (FEG), operated at 3 kV.
Multiwalled carbon nanotubes (MWNT) (diameter 15±5 nm;
length 1–5 µm) were purchased from Nano-Lab and were used
without further purification.
Acetonitrile (MeCN), dichloromethane (DCM), 1,4-dioxane, and
other organic solvents used were spectroscopic grade. These
solvent were distilled from appropriate drying agents (CaH2 and
CaCl2) under argon just prior to use. The water used in catalysis is
grade Milli-Q.
Raman scattering spectra were collected on a Horiba Jobin
Yvon Dilor XY 800 confocal microspectrometer, equipped with a
CCD detector of 1024×256 pixels, a holographic grating of 2400
groves/mm and a 50-mW Ar laser (413 nm wavelength) as excitation
source. Spectra were measured in the 100–1600 cm−1 Raman shift
-
Instruments
All electrochemical measurements were performed with a TEQ
03 potentiostat, with a standard 3-electrode set up. For cyclic
8
This article is protected by copyright. All rights reserved.

10.1002/cctc.201700349
ChemCatChem
FULL PAPER
region, at 1 cm−1 spectral resolution. Measurements were carried out
in conditions of high confocality (3 pixels of the CCD detector and 20
with chloroform to remove the molecules of corrole not absorbed on
the nanotube surface.
µm slit width) through
a 100× Leica metallurgical objective
-
Determination of the amount of adsorbed corroles on the
nanotubes
(numerical aperture of 0.9), which limits the diameter of the laser
beam to about 1µm. All spectra were baseline corrected.
The amount of adsorbed corroles on the nanotubes surface
was measured by un-absorbing and separating the corroles from the
nanotubes using a column of neutral alumina. Then, the obtained
corrole solution was evaporated and the solid was dissolved in 2.5
mL of DCM. The concentration was calculated by measuring the
absorbance of this solution at 422 nm and using the Lambert-Beer
law: A = ε. l. [C]. Where: ε = 98.2×103 M/cm; l = 1 cm; and [C] =
corrole molar concentration. The procedure was repeated three
times for each nanocomposite and the average value was expressed.
-
Metallocorrole and metalloporphyrin synthesis
Corroles: tris-phenyl-Corrole (TP-Cor); and tris-(2,6-dichloro-phenyl)-
Corrole, (Cl2-Cor) were synthesized by the method described by
Gryko et al.[14] While tris-(p-NO2-phenyl)-Corrole, (NO2-Cor) was
prepared following the procedure by Paolesse et al.[65] To diminish
oxidative degradation of the corroles[65,66], purification was performed
by protecting chromatographic columns from light, and the products
were stored under inert atmosphere. The purification step with silica
gel column (63-200 μm and 70-230 mesh) was optimized, and the
eluents used were: CHCl3 for TP-Cor; CH2Cl2: n-hexane (1:2) for Cl2-
Cor; and CH2Cl2 for NO2-Cor. The main spectroscopic and
electrochemical parameters of the obtained ligands are summarized
in Table S3.
-6
The calculated [C] was 4.73×10 M. So, for a volume of 2.5 mL,
the amount of corrole was (1.22±0.13)×10-10 mol. This calculation
was done in triplicate and the reproducibility was check. The mass of
NO2-Cor-Co calculated was (0.84
±
0.21)μg, representing,
approximately the (0.06 ± 0.02) % of the total weight of the
nanocomposite initial mass (1.4 ± 0.1) mg.
Cobalt-corroles: To obtain the cobalt complexes, the synthetic route
described by Guilard et al.[67] was used. Cobalt (II) acetate
tetrahydrate and corrole were mixed in a 3:1 ratio and refluxed in a
mixture of chloroform/methanol (7:3) for 90 min. The reaction was
followed by UV-Vis. The obtained metallocorroles were purified with
-
Photocatalytic and Photoelectrocatalytic experiments
Photocatalytic experiments were done with a medium pressure
mercury (Hg) lamp. The light emitted is bluish-white color, contains
no red radiation. Mercury lamps have various emission lines in both
the visible and UV with considerable intensity. For this work the line
is located at 253 nm excites the LMCT band of the corroles, located
at ca. 200-250 nm.
a
basic alumina column using DCM as eluent. The main
spectroscopic and electrochemical parameters of the obtained
metallocomplexes are summarized in Table S1.
Iron-corroles: These complexes were obtained by using the
technique described by Walker et al.[68] Iron (II) chloride and the
corroles were mixed in 5:1 ratio and refluxed in dimethylformamide
(DMF) under inert atmosphere for 45 min. The reaction was followed
by UV-Vis. The purification was carried out performing an acid-base
extraction, and the organic fraction was then filtered through a short
column of neutral alumina. The elution solvent differed depending on
the metalocorrole: for TP-Cor-Fe, CHCl3 was used and for Cl2-Cor-
Fe and NO2-Cor-Fe, pure DCM was used. The main spectroscopic
and electrochemical parameters of the obtained metallocomplexes
are summarized in Table S1.
Photoelectrocatalytic experiments were performed combining
amperometry at -450 mV vs. Ag°/AgCl with irradiation by the Hg
lamp. Two conditions were studied: a) deoxygenated 1,4-dioxane
solutions containing TEA (5 vol %) and TP (3 mmol.L-1); and b)
formiate buffer pH 3, 0.1 M. Blanks in all cases (with no catalyst)
were performed and no gas formation was observed. Experiments
were performed in triplicate. Amount of catalyst used: 1.2×10-10 mol.
Blank experiments performed with no catalyst gas production
was not observed. Evolved H2 volume measurements were
performed using 7.5x10-6 moles of catalyst and 2 successive aliquots
of 200 µL of water. No gas production was obtained with
experiments performed with no UV light or with filters that did not
allow the passage of wavelength below 375 nm.
-
Preparation of MWNT-corrole nanocomposites
MWNT (10 mg) were sonicated in nitric acid (35 vol %) (25 mL) with
a sonic bath (120 W max) (100% for 5 min and then 40% for 15 min)
and then heated at 60°C for 12 h. The suspension was then cooled;
vacuum filtered and washed with water. The nanotubes were
redispersed in NaOH 2 M (100 mL) using the sonic bath (100% for
10 min) and then filtered and washed with deionized water, and then
HCl 1 M followed by deionized water until the filtrate was neutral.
Secondly, the MWNT were centrifuged and redispersed by
sonication in the corrole chloroformic solution. After 12 h the MWNT-
corrole nanocomposite was separated by centrifugation and washed
-
Measurements of H2 production
A Shimadzu-14A gas chromatograph with Thermal conductivity
detector (TCD) was employed for the analytical quantification of H2.
This was equipped with two packed columns of stainless steel, one
internal and other external to the gas chromatograph. The output of
the first column of 2 m long and 3 mm ID was connected to a
channel of the detector. The second column of 0.5 m long and 3 mm
ID, connected in series, was submerged in a bath of ethanol-liquid
9
This article is protected by copyright. All rights reserved.

10.1002/cctc.201700349
ChemCatChem
FULL PAPER
nitrogen mix. The output was connected to the reference channel of
the detector, previously passing through the oven to take the same
temperature. Both columns were filled with Molecular Sieve 13X. The
columns operating temperatures were 110 °C for the internal and -
100 °C for the external column. The detector temperature was 110
°C. As gas carrier, nitrogen chromatographic quality was used, at a
pressure of 2 kg/cm2 at the head of the column. The system for the
introduction of sample consisted of a 6-way valve with a loop of 1 mL
(Valco Instrument Co. Inc.) attached to a glass manometer of Hg of
two branches. The entire system was connected, through a needle
valve, to a vacuum pump made for LEYBOLD GmbH (model MINI A)
working at room temperature of 24 °C. This system allows the
transfer the gas sample in a container of fixed volume to the loop,
and the introduction to the chromatograph. Successive injections at
different pressures, allows the replicated of same sample. For the
acquisition interface from Data Apex Co. (model U-PAD2 USB) was
used with Clarity Lite Software for data analysis. Figure S2 shows
the experimental setup for this step. Amount of catalyst used:
1.2×10-9 mol.
1999, 38, 1427–1429.
[12]
[13]
Z. Gross, N. Galili, L. Simkhovich, I. Saltsman, M.
Botoshansky, D. Bläser, R. Boese, I. Goldberg, Org. Lett.
1999, 1, 599–602.
R. Paolesse, S. Mini, F. Sagone, T. Boschi, L. Jaquinod, D.
J. Nurco, K. M. Smith, Chem. Commun. 1999, 1307–1308.
D. T. Gryko, Chem. Commun. 2000, 2243–2244.
D. T. Gryko, K. Jadach, J. Org. Chem. 2001, 66, 4267–
4275.
[14]
[15]
[16]
[17]
[18]
R. M. Kellett, T. G. Spiro, Inorg. Chem. 1985, 24, 2373–
2377.
M. A. Morales Vásquez, S. A. Suárez, F. Doctorovich,
Mater. Chem. Phys. 2015, 159, 159–166.
R. K. Hocking, S. D. George, Z. Gross, F. A. Walker, K. O.
Hodgson, B. Hedman, E. I. Solomon, Inorg. Chem. 2009,
48, 1678–1688.
F. M. Toma, A. Sartorel, M. Iurlo, M. Carraro, P. Parisse, C.
Maccato, S. Rapino, B. R. Gonzalez, H. Amenitsch, T. Da
Ros, et al., Nat. Chem. 2010, 2, 826–831.
F. Li, L. Li, L. Tong, Q. Daniel, M. Göthelid, L. Sun, Chem.
Commun. 2014, 50, 13948–13951.
H. Li, B. Zhou, Y. Lin, L. Gu, W. Wang, K. A. S. Fernando,
S. Kumar, L. F. Allard, Y.-P. Sun, J. Am. Chem. Soc. 2004,
126, 1014–1015.
G. Bottari, G. de la Torre, T. Torres, Acc. Chem. Res. 2015,
48, 900–910.
[19]
[20]
[21]
[22]
[23]
F. D’Souza, R. Chitta, A. S. D. Sandanayaka, N. K.
Subbaiyan, L. D’Souza, Y. Araki, O. Ito, J. Am. Chem. Soc.
2007, 129, 15865–15871.
[24]
[25]
[26]
D. M. Guldi, G. M. A. Rahman, F. Zerbetto, M. Prato, Acc.
Chem. Res. 2005, 38, 871–878.
Y. Tachibana, L. Vayssieres, J. R. Durrant, Nat. Photonics
2012, 6, 511–518.
Y. Cheng, A. Memar, M. Saunders, J. Pan, C. Liu, J. D.
Gale, R. Demichelis, P. K. Shen, S. P. Jiang, J. Mater.
Chem. A 2016, 4, 2473–2483.
I. Hijazi, T. Bourgeteau, R. Cornut, A. Morozan, A. Filoramo,
J. Leroy, V. Derycke, B. Jousselme, S. Campidelli, J. Am.
Chem. Soc. 2014, 136, 6348–6354.
The gas (H2) production was determined by connecting the reaction
cell with a gas burette (25.0  0.5 mL), which’s lower end is
connected by a hose to an ampoule and all system is sealed with
Hgº. All volumes reported in this paper were taken at atmospheric
pressure as the internal pressure is equalized with the outside.
Figure S1 shows the experimental setup for this step. Amount of
catalyst used: 1.2×10-10 mol.
[27]
[28]
Q. Zhong, V. V. Diev, S. T. Roberts, P. D. Antunez, R. L.
Brutchey, S. E. Bradforth, M. E. Thompson, ACS Nano
2013, 7, 3466–3475.
Acknowledgements
[29]
[30]
[31]
[32]
[33]
A. Choi, H. Jeong, S. Kim, S. Jo, S. Jeon, Electrochim. Acta
2008, 53, 2579–2584.
W. Tu, J. Lei, H. Ju, Electrochem. commun. 2008, 10, 766–
769.
This work was financially supported by CONICET (PIP 112 201001
00125). MAMV and AYT thank CONICET for a fellowship grant. NIN,
MH, EJC and FD are members of CONICET.
F. Li, B. Zhang, X. Li, Y. Jiang, L. Chen, Y. Li, L. Sun,
Angew. Chemie 2011, 123, 12484–12487.
T. Dhanasekaran, J. Grodkowski, P. Neta, P. Hambright, E.
Fujita, J. Phys. Chem. A 1999, 103, 7742–7748.
J. Grodkowski, P. Neta, E. Fujita, A. Mahammed, L.
Simkhovich, Z. Gross, J. Phys. Chem. A 2002, 106, 4772–
4778.
B. Ramdhanie, J. Telser, A. Caneschi, L. N. Zakharov, A. L.
Rheingold, D. P. Goldberg, J. Am. Chem. Soc. 2004, 126,
2515–2525.
S. Matsuoka, T. Kohzuki, C. Pac, A. Ishida, S. Takamuku,
M. Kusaba, N. Nakashima, S. Yanagida, J. Phys. Chem.
1992, 96, 4437–4442.
D. Behar, T. Dhanasekaran, P. Neta, C. M. Hosten, D. Ejeh,
P. Hambright, E. Fujita, J. Phys. Chem. A 1998, 102, 2870–
2877.
Z. Ou, A. Lü, D. Meng, S. Huang, Y. Fang, G. Lu, K. M.
Kadish, Inorg. Chem. 2012, 51, 8890–8896.
D. N. Hendrickson, M. G. Kinnaird, K. S. Suslick, J. Am.
Chem. Soc. 1987, 109, 1243–1244.
B. Mondal, K. Sengupta, A. Rana, A. Mahammed, M.
Botoshansky, S. G. Dey, Z. Gross, A. Dey, Inorg. Chem.
2013, 52, 3381–3387.
Keywords: photocatalysis; electrocatalysis; metallocorroles;
hydrogen; synthesis; water splitting.
[1]
K. Peuntinger, T. Lazarides, D. Dafnomili, G. Charalambidis,
G. Landrou, A. Kahnt, R. P. Sabatini, D. W. McCamant, D.
T. Gryko, A. G. Coutsolelos, et al., J. Phys. Chem. C 2013,
117, 1647–1655.
[34]
[35]
[36]
[2]
[3]
[4]
H.-Y. Liu, M. H. Mahmood, S.-X. (Samuel) Qiu, C. K. Chang,
Coord. Chem. Rev. 2013, 257, 1306–1333.
D. T. Gryko, J. P. Fox, D. P. Goldberg, J. Porphyr.
Phthalocyanines 2004, 8, 1091–1105.
E. Vogel, S. Will, A. S. Tilling, L. Neumann, J. Lex, E. Bill, A.
X. Trautwein, K. Wieghardt, Angew. Chemie Int. Ed. English
1994, 33, 731–735.
[37]
[38]
[39]
[5]
S. Will, J. Lex, E. Vogel, H. Schmickler, J.-P. Gisselbrecht,
C. Haubtmann, M. Bernard, M. Gorss, Angew. Chemie Int.
Ed. English 1997, 36, 357–361.
[6]
[7]
Z. Gross, JBIC J. Biol. Inorg. Chem. 2001, 6, 733–738.
A. Mahammed, J. J. Weaver, H. B. Gray, M. Abdelas, Z.
Gross, Tetrahedron Lett. 2003, 44, 2077–2079.
H. Park, C. D. Vecitis, W. Choi, O. Weres, M. R. Hoffmann,
J. Phys. Chem. C 2008, 112, 885–889.
L. Shi, H.-Y. Liu, H. Shen, J. Hu, G.-L. Zhang, H. Wang, L.-
N. Ji, C.-K. Chang, H.-F. Jiang, J. Porphyr. Phthalocyanines
2009, 13, 1221–1226.
[40]
[41]
[42]
[43]
Z. Wang, H. Lei, R. Cao, M. Zhang, Electrochim. Acta 2015,
171, 81–88.
[8]
[9]
J. Wang, Y. Chen, W. J. Blau, J. Mater. Chem. 2009, 19,
7425.
D. Baskaran, J. W. Mays, X. P. Zhang, M. S. Bratcher, J.
Am. Chem. Soc. 2005, 127, 6916–6917.
G. A. M. Sáfar, H. B. Ribeiro, L. M. Malard, F. O. Plentz, C.
Fantini, A. P. Santos, G. de Freitas-Silva, Y. M. Idemori,
[10]
[11]
I. Aviv-Harel, Z. Gross, Coord. Chem. Rev. 2011, 255, 717–
736.
Z. Gross, N. Galili, I. Saltsman, Angew. Chemie Int. Ed.
10
This article is protected by copyright. All rights reserved.

10.1002/cctc.201700349
ChemCatChem
FULL PAPER
Chem. Phys. Lett. 2008, 462, 109–111.
[44]
G. Magadur, J.-S. Lauret, V. Alain-Rizzo, C. Voisin, P.
Roussignol, E. Deleporte, J. A. Delaire, ChemPhysChem
2008, 9, 1250–1253.
[45]
[46]
[47]
[48]
[49]
[50]
[51]
[52]
[53]
G. A. Rance, D. H. Marsh, R. J. Nicholas, A. N. Khlobystov,
Chem. Phys. Lett. 2010, 493, 19–23.
J. Yu, N. Grossiord, C. E. Koning, J. Loos, Carbon N. Y.
2007, 45, 618–623.
A. G. Ryabenko, T. V. Dorofeeva, G. I. Zvereva, Carbon N.
Y. 2004, 42, 1523–1535.
P. Huang, C. Xu, J. Lin, C. Wang, X. Wang, C. Zhang, X.
Zhou, S. Guo, D. Cui, Theranostics 2011, 1, 240–250.
E. Steene, T. Wondimagegn, A. Ghosh, J. Inorg. Biochem.
2002, 88, 113–118.
K. Lewandowska, B. Barszcz, J. Wolak, A. Graja, M.
Grzybowski, D. T. Gryko, Dye. Pigment. 2013, 96, 249–255.
I. H. Wasbotten, T. Wondimagegn, A. Ghosh, J. Am. Chem.
Soc. 2002, 124, 8104–8116.
T. Odedairo, J. Ma, Y. Gu, J. Chen, X. S. Zhao, Z. Zhu, J.
Mater. Chem. A 2014, 2, 1418–1428.
I. Pócsik, M. Hundhausen, M. Koós, L. Ley, J. Non. Cryst.
Solids 1998, 227–230, P, 1083–1086.
[54]
[55]
L. Bokobza, Express Polym. Lett. 2012, 6, 601–608.
V. A. Karachevtsev, E. S. Zarudnev, S. G. Stepanian, A. Y.
Glamazda, M. V. Karachevtsev, L. Adamowicz, J. Phys.
Chem. C 2010, 114, 16215–16222.
[56]
[57]
[58]
[59]
T. A. Saleh, V. K. Gupta, J. Colloid Interface Sci. 2011, 362,
337–344.
J. E. Riggs, Z. Guo, D. L. Carroll, Y.-P. Sun, J. Am. Chem.
Soc. 2000, 122, 5879–5880.
D. M. Guldi, H. Taieb, G. M. A. Rahman, N. Tagmatarchis,
M. Prato, Adv. Mater. 2005, 17, 871–875.
F. D’Souza, S. K. Das, M. E. Zandler, A. S. D.
Sandanayaka, O. Ito, J. Am. Chem. Soc. 2011, 133,
19922–19930.
[60]
[61]
[62]
[63]
[64]
[65]
[66]
[67]
[68]
J. L. Dempsey, B. S. Brunschwig, J. R. Winkler, H. B. Gray,
Acc. Chem. Res. 2009, 42, 1995–2004.
S. Losse, J. G. Vos, S. Rau, Coord. Chem. Rev. 2010, 254,
2492–2504.
Y. Sun, J. P. Bigi, N. A. Piro, M. L. Tang, J. R. Long, C. J.
Chang, J. Am. Chem. Soc. 2011, 133, 9212–9215.
H. I. Karunadasa, E. Montalvo, Y. Sun, M. Majda, J. R.
Long, C. J. Chang, Science (80-. ). 2012, 335, 698–702.
H. I. Karunadasa, C. J. Chang, J. R. Long, Nature 2010,
464, 1329–1333.
R. Paolesse, S. Nardis, F. Sagone, R. G. Khoury, J. Org.
Chem. 2001, 66, 550–556.
J. Wojaczyński, M. Duszak, L. Latos-Grażyński,
Tetrahedron 2013, 69, 10445–10449.
J.-M. Barbe, G. Canard, S. Brandes, F. Jerome, G. Dubois,
R. Guilard, Dalt. Trans. 2004, 1208–1214.
F. A. Walker, S. Licoccia, R. Paolesse, J. Inorg. Biochem.
2006, 100, 810–837.
11
This article is protected by copyright. All rights reserved.

10.1002/cctc.201700349
ChemCatChem
FULL PAPER
FULL PAPER
Text for Table of Contents:
Key Topic: Catalysis
Abstract
Miguel A. Morales Vásquez, Mariana
Hamer, Nicolás I. Neuman, Alvaro Y.
Tesio, Andrés Hunt, Horacio Bogo,
Ernesto J. Calvo and Fabio Doctorovich*
Introduction
Result and discussion
Conclusions
Experimental section
Acknowledgements
Keywords
Page No. – Page No.
Title:
References
Iron and cobalt corroles in solution and
on carbon nanotubes as molecular
photocatalysts for hydrogen production
by water reduction
12
This article is protected by copyright. All rights reserved.