A General Synthesis of Porous Carbon Nitride Films with Tunable Surface Area and Photophysical Properties

Article abstract of DOI:10.1002/anie.201711669

Graphitic carbon nitride (g-CN) has emerged as a promising material for energy-related applications. However, exploitation of g-CN in practical devices is still limited owing to difficulties in fabricating g-CN films with adjustable properties and high surface area. A general and simple pathway is reported to grow highly porous and large-scale g-CN films with controllable chemical and photophysical properties on various substrates using the doctor blade technique. The growth of g-CN films, ascribed to the formation of a supramolecular paste, comprises g-CN monomers in ethylene glycol, which can be cast on different substrates. The g-CN composition, porosity, and optical properties can be tuned by the design of the supramolecular paste, which upon calcination results in a continuous porous g-CN network. The strength of the porous structure is demonstrated by high electrochemically active surface area, excellent dye adsorption and photoelectrochemical and photodegradation properties.

Full text of DOI:10.1002/anie.201711669

A Journal of the Gesellschaft Deutscher Chemiker
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Accepted Article
Title: A General Synthesis of Porous Carbon Nitride Films with Tunable
Surface Area and Photophysical Properties
Authors: Guiming Peng, Lidan Xing, Jesus Barrio, Michael Volokh, and
Menny Shalom
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To be cited as: Angew. Chem. Int. Ed. 10.1002/anie.201711669
Angew. Chem. 10.1002/ange.201711669
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10.1002/anie.201711669
Angewandte Chemie International Edition
COMMUNICATION
A General Synthesis of Porous Carbon Nitride Films with Tunable
Surface Area and Photophysical Properties
Guiming Peng, Lidan Xing, Jesús Barrio, Michael Volokh, and Menny Shalom*
Abstract: Graphitic carbon nitride (g-CN) has emerged as a promising
material for energy-related applications. However, exploitation of g-CN in
practical devices is still limited due to the difficulty in fabricating g-CN films
with adjustable properties and high surface area. Here we report a general
and simple pathway to grow highly porous and large-scale g-CN films with
controllable chemical and photophysical properties on various substrates
using doctor blade technique. The growth of g-CN films is ascribed to the
formation of supramolecular paste, comprises g-CN monomers in ethylene
glycol, which can be cast on different substrates. The g-CN composition,
porosity, and optical properties can be easily tuned by the design of the
supramolecular paste, which upon calcination results in a continuous porous
g-CN network. The strength of the porous structure is demonstrated by high
electrochemical active surface area, excellent dye adsorption,
photoelectrochemical and photodegradation properties.
This technique was previously described for the deposition of g-CN
powder on FTO for photoelectrochemical applications.[13] However, the
deposition of g-CN monomers that can be converted in a controlled
manner into the final g-CN film has never been reported before. This
technique requires the formation of a homogeneous paste that can be cast
on
a
substrate. The paste usually includes some organic
molecules/polymers that bind the particles (e.g. TiO2). Then, the paste is
cast on the substrate, followed by a thermal treatment at high
temperature under air or inert atmosphere. However, the fabrication of
g-CN films by this method is challenging due to (i) the difficulty in
achieving a homogeneous paste composed of g-CN or g-CN monomers,
and (ii) the possible carbonization of the binders at higher temperature,
which may change the final materials’ composition.
Here we demonstrate a simple and versatile method to fabricate
large-scale and highly porous g-CN films with controllable thickness
and composition on various substrates ranging from FTO, Al foil, porous
TiO2, silicon wafer, and glass, using doctor blade technique. Uniform
supramolecular pastes of g-CN monomers in ethylene glycol (EG) were
prepared and transferred onto various substrates. Upon calcination, they
afforded uniform g-CN layers with high surface area according to the
electrochemical surface area and dye adsorption measurements. The
films exhibit excellent dye degradation and good photoelectrochemical
properties under white-light illumination.
Melon based graphitic carbon nitride (g-CN), a low-cost and
environmentally friendly semiconductor, has attracted enormous interest
over the past years due to its unique electronic and photophysical
properties, which have been exploited in various fields, such as photo-
and electro-catalysis,[1] heterogeneous catalysis,[2] batteries,[3] light-
emitting diodes,[4] solar cells,[5] and sensing.[6] Substantial research has
been devoted to the synthesis of carbon nitride as a powder,[7] and a
significant progress has been achieved using hard and soft templating
methods,[7c, 7f] heteroatoms doping,[1k, 8], copolymerization,[9] and self-
assembly of g-CN monomers prior to their calcination at high
temperatures.[7a, 7b, 7e] However, exploitation of g-CN in device-related
applications, such as batteries, electrolyzers, solar cells, and light
emitting diodes, is still limited due to the difficulty in fabricating g-CN
with adjustable properties and high surface area on different substrates.
Recently, several methods to grow g-CN on substrates were
introduced, based on the deposition of preformed g-CN powder,[10] or by
direct growth of g-CN on various substrates.[11] On the one hand, while
well-established synthetic tools have given access to g-CN powders with
a range of tailored properties, the poor solubility of g-CN in most
solvents required the use of strong acids to disperse it in a liquid for
coating,[10a] which makes the deposition only possible onto inert
substrates and materials. Moreover, the deposited g-CN powder usually
forms a weak physical contact with the substrate. On the other hand,
while the direct growth of g-CN, mainly by vapor-assisted methods,
does result in the formation of compact and continuous g-CN layers with
an intimate contact with the substrate,[11a, 11b] controlling the final g-CN
composition and properties is still difficult due to the limited range of
precursors adapted to the gas phase reaction. Furthermore, it results in a
compact layer with a relatively low surface area, preventing its
utilization in fields which require a more accessible structure. Therefore,
it is of great interest to develop a general method to fabricate porous and
continuous g-CN layer with not only an intimate contact with a range of
substrates, but also a controllable thickness as well as tunable chemical
and photophysical properties.
Figure 1. (a) Schematic illustration of doctor blade preparation method, (b-e) SEM
images of supramolecular precursors films prepared from (b) CMBA(0), (c)
CMBA(0.05), (d) CMBA(0.1), and (e) CMBA(0.15). The cross-sectional SEM images
of the corresponding films are shown in the inset of the images.
The schematic illustration of g-CN film is presented in Figure 1a,
while the experimental details are given in Supporting Information (SI).
The supramolecular paste was prepared by mixing 1.29 g cyanuric acid
(C), 1.26 g melamine (M) and a small amount of barbituric acid (BA) in
water, denoted here as CMBA(x) where x=0, 0.05, 0.1, 0.15 refers to the
mass of BA in the supramolecular precursor. In the next step, the water
was removed, and the CMBA(x) powder was re-dispersed and ground
in EG, forming a stable milky paste (Figure S1). It is reported that EG
can be used as a binder in dispersing inorganic components as pastes.[14]
The paste was cast onto FTO, resulting in uniform and compact
supramolecular films (insets in Figure 1(b-e)). The morphologies and
the thicknesses of the deposited CMBA(x) pastes are presented in Figure
1(b-e). We found that the addition of BA into the precursors helps the
film to be slightly flatter and more continuous. The thickness of CMBA
films is ~17 μm (insets in Figure 1(b-e)). Overall, for the supramolecular
films, no peeling off from the FTO is observed, suggesting the successful
deposition of CMBA(x) supramolecular paste onto FTO. Fourier
transform infrared spectroscopy (FTIR) was used to confirm the
Doctor blade technique is a common and straightforward method
to fabricate large-scale and porous metal-oxides and carbon films.[12]
[*]
Dr. G. Peng, J. Barrio, Dr. M. Volokh, Prof. M. Shalom
Department of Chemistry and Ilse Katz Institute for Nanoscale
Science and Technology, Ben-Gurion University of the Negev, Beer-
Sheva 8410501, Israel.
E-mail: mennysh@bgu.ac.il
Prof. L. Xing,
School of Chemistry and Environment, South China Normal
University, Guangzhou 510006, China.
Supporting information for this article can be found via:
www.onlinelibrary.wiley.com
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10.1002/anie.201711669
Angewandte Chemie International Edition
COMMUNICATION
formation of a supramolecular assembly (Figure S2). The C=O peak of
cyanuric acid at 1683 cm-1 is split into two peaks at 1656 cm-1 and 1725
cm-1, and the vibration peak of the triazine ring in melamine is shifted
incorporation of 0.05 g BA in the starting supramolecular paste, a well-
defined continuous g-CN nanowires network is formed (Figure 2d).
Higher magnification SEM imaging shows that the nanowires are
constructed from very small nanoparticles (Figure S7). The networks
structure is preserved with the increase of BA amount, while the pore
size is moderately decreased (Figure 2e and 2f). The pores across the
vertical direction are relative smaller compared to the top surface,
meaning that the g-CN network is better packed along the vertical
direction. The anisotropic porosity should allow better connection
between the g-CN layers while keeping high accessible surface area. The
thickness of the films is ~8 μm for all the BA-doped g-CN films and ~16
μm for the g-CN(0). The exception for g-CN(0) may originate from the
different crystals size of the precursors (Figure 1b and Figure S5). The
decrease in thickness of the final g-CN films compared to the starting
supramolecular films (Figure 1(b-e)) is due to the condensation process
which involves gas release and shrinkage of the structure. The thickness
of the supramolecular assembly films and subsequently the final g-
CN(x) films can be easily varied by the number of scotch-tape layers,
and it is directly proportional to the number of scotch-tape layers as
shown in Figure S8. By using two scotch-tape layers, the final thickness
of g-CN(x) films is almost doubled (~22 μm) (Figure S9).
from 809 cm-1 to 763 cm-1, indicating the establishment of
supramolecular assembly.
a
Density functional theory (DFT) calculation reveals that EG
establishes two parallel hydrogen bonds with cyanuric acid (Figure S3f,
some possible interaction configurations and the interaction energies
(Eint) are summarized in Figure S3). In addition, our results indicate that
each EG molecule can interlink with two molecules of cyanuric acid
through the two terminal hydroxyl groups (Eint almost doubles compared
to one-end connection (79.0 kJ/mol vs 40.1 kJ/mol)) (Figure S3(b, g)).
The latter indicates the strong binding of EG to the supramolecular
assembly, and further explains the formation of a viscous paste (further
discussion is given in the supporting information). Hydrogen bonds
between the cyanuric acid and EG would weaken the H-bond in CM,
thus releasing part of the melamine amine groups (Figure S3f and Figure
S4). In good accordance with the theory, FTIR measurement shows the
appearance of a NH2 peak at 3466 cm-1 after incorporation with EG
(Figure S2b). The addition of BA introduces more available carbonyl
groups, which can further react with melamine and EG, resulting in the
disappearance of the above -NH2 peak. Another proof for the integration
of the EG and BA within the supramolecular assembly is given by the
pronounced changes in the crystal structure of the assemblies as shown
in Figure S5. Compared to CMBA(0), the addition of BA results in the
disappearance of the XRD peaks at ~20°, ~30°, and the enhancement of
the peak at 10.7° (Figure S5a), attributed to stronger interplanar stacking
and the in-plane rearrangement, respectively. All the above-mentioned
data strongly indicates that the BA and EG are fully integrated within
the assembly.
Thermal gravimetric analysis (TGA) was used to investigate the
growth mechanism of g-CN from the paste, as well as the role of BA
during calcination (Figure S10). The TGA measurements reveal that the
first significant weight loss of the CMBA(0.05) paste occurs at higher
temperature (~400 °C), compared to the CM paste (~300 °C). This
further specifies that the BA stabilizes the supramolecular assembly and
prevents the partial decomposition of the monomers prior to their
condensation.
To transform the CMBA(x) films into g-CN, the supramolecular
films were calcinated for 4 h at 550 °C in a closed 16 mm-diameter glass
tube under N2 atmosphere. Following this method, uniform and
transparent g-CN films on FTO (marked as g-CN(x), x=0, 0.05, 0.1, 0.15,
respectively) were successfully obtained (Figure 2a). UV-vis absorbance
measurements (Figure 2b) show steep absorption edges for all films,
indicating their strong semiconductor characteristics. The onset
absorption edge of g-CN(0) is at ~460 nm, which corresponds to a
bandgap of 2.7 eV (Figure 2b). The BA doping leads to a red shift of the
absorption (Figure 2a) due to a higher carbon content in the final g-
CN.[15] The photoluminescence of all the g-CN(x)s is quenched
compared to the g-CN(0) due to the increase of carbon in the final g-CN
(Figure S6), which leads to heterojunction formation and non-radiative
recombination paths.[15]
Figure 3. Characterizations of the carbon nitride films on FTO. (a) FTIR spectra. (b)
C1s XPS. (c) N1s XPS.
The structure and composition of the films were further
investigated by FTIR, elemental analysis (EA), X-ray diffraction (XRD),
and X-ray photoelectron spectroscopy (XPS). FTIR spectra (Figure 3a)
show the stretching modes of g-CN heterocycles between 1200 cm-1 and
1600 cm-1, while the breathing mode peak of the triazine units appears
at ~800 cm-1.[16] No prominent differences can be found for the different
g-CN films in the FTIR spectra. EA results reveal that the C/N ratio
increases at higher BA amount in the starting assemblies (Table S1).
XPS was used to track the chemical states changes in the porous g-CN(x).
The high resolution XPS of C1s (Figure 3b) presents two typical peaks
at 284.8 and 288.2 eV that can be assigned to the sp2 C in carbonaceous
environment and sp2 C in C-N heterocycles, respectively.[17] The
integration of BA in the starting supramolecular assemblies results in the
increase of the peaks at 284.8 eV and 286.5 eV due to the formation C-
C and C-N bonds in the final g-CN(x), respectively, in consistence with
EA results. The N1s XPS spectra of the g-CN(x) can be deconvoluted
into three peaks, 398.7 eV (C=N-C), 400 eV (N-C3), and 400.9 eV (C-
NH-C and C-NH2).[17a] The formation of g-CN is also confirmed by
XRD pattern and a weak in-planar peak at ~12° (100), and inter-planar
stacking peak at ~27° (002) can be observed for the thick films (Figure
S11). However, due to the low crystallinity of the g-CN(x) layer,
compared to the FTO, almost no signal can be discerned from XRD
patterns of the thinner films.
Figure 2. (a) Images of g-CN(x) films on FTO. (b) UV-vis absorbance spectra of g-
CN(x) electrodes. (c-f) SEM images of g-CN(x) films: (c) g-CN(0), (d) g-CN(0.05), (e)
g-CN(0.1), (f) g-CN(0.15).
SEM images of all the films demonstrate that the g-CN
homogeneously covers the FTO (Figure 2(c-f)). The morphology
became more ordered for the BA-doped films, due to the higher stability
of BA compared to cyanuric acid at high temperatures. After
It is important to note that for all films, the g-CN network is
strongly attached to the FTO. The interaction between the g-CN(0.05)
and FTO was evaluated by FTIR and XPS measurements of the FTO/g-
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10.1002/anie.201711669
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COMMUNICATION
CN interface after removal of the g-CN(0.05) layer by a strong
sonication (Figure S12(a-d) and Figure S13). The results disclose that
the g-CN is bonded to the FTO surface via FTO-O-NH- bond.[18] The
strong interaction could also be verified by the direct growth of g-
CN(0.05) wires on the FTO surface (Figure S12e).
Melamine formed a non-homogeneous paste with large grain boundaries,
leading to non-uniform g-CN film after calcination (Figure S26). The
cyanuric acid formed an acceptable paste, further accentuating the strong
interaction with EG as shown in Figure S3(b, c). However, we could not
obtain any g-CN after calcination probably due to the decomposition of
cyanuric acid at high temperatures (Figure S27). As a proof of concept,
the generality of this method is successfully demonstrated by the
utilization of other supramolecular precursors, such as cyanuric acid /2,
4-diamine-6-phenyl-1,3,5-triazine (1:1, molar ratio), and melamine
/barbituric acid (1:1, molar ratio) supramolecular assemblies (Figure
S28).
The electrochemically active surface area (ECSA) is an important
parameter that can indicate the potential of materials in electrochemical
devices.[21] The ECSA for each g-CN film was evaluated by double-layer
capacitance measurements (Figure 5a and Figure S29). The insertion of
BA results in a sheer increase of the double-layer capacitance of the g-
CN(x) films, in agreement with the porous morphology observed in
SEM images. The g-CN(0.15) reaches up to 102-fold higher ECSA
compared to the bare FTO, proving the high surface area of the films.
The internal surface area can be also characterized as a roughness factor
(RF), which is defined as the ratio of actual surface area to the projection
area of the film.[22] To facilitate the determination of RF, we measured
methylene blue (MB) adsorption on the surface of a ~20 cm2 (the exact
sizes are given in Table S2) thick g-CN films (~22 μm). After 24-hours
incubation of g-CN(x) in 10-5 g/mL MB aqueous solution, all the g-
CN(x) films were blue-colored (Figure S30). The RF of all g-CN(x)
films were calculated by assuming a monolayer dye adsorption on g-CN
surface (see experimental section for more details) and are summarized
in Figure 5b and Table S2. All g-CN films demonstrate relatively high
RF, ranging from 85 to 140. In agreement with the ECSA, the RF also
increases with the insertion of BA. From the ECSA and RF
measurements we can conclude that the fabricated g-CN(x) films have a
porous structure with high specific surface area.
The influence of other solvents on the paste formation and the final
morphology of g-CN were studied by replacing EG with 2-propanol
(IPA), dimethyl sulfoxide (DMSO), and N,N-dimethylformamide
(DMF). The IPA-based paste yields a much looser g-CN networks
(Figure S14) compared to the EG one, due to the presence of one
hydroxyl group only. This further emphasizes the binding effect of the
two terminal hydroxyl groups in EG. Interestingly, the use of aprotic
solvents (DMSO and DMF) that act as hydrogen acceptors with strong
binding energies to the supramolecular monomers (see DFT simulation,
Figure S15) also leads to homogeneous paste formation and similar
morphologies of g-CN(0.05) films after calcination (Figure S16).
To show the generality of this method, g-CN with different atomic
compositions was successfully grown on aluminum foil, silicon wafer,
glass slide, and TiO2 electrode (Figure 4, Figures S17-S19). The g-
CN(0) on aluminum foil, silicon wafer, and glass slide exhibit strong
fluorescence upon illumination with 365 nm UV light (Figure 4(a-d)).
To investigate the influence of the substrates on the g-CN morphology,
SEM images of g-CN(0.05) on different substrates were examined
(Figure S17). The g-CN(0.05) on aluminum foil and silicon wafer has a
continuous networks composed of nanowires morphology, similar to the
one on FTO. Interestingly, a smoother and less porous structure is
obtained on a glass slide (Figure S17b). It is important to note that the
calcination of CMBA(0.05) paste powder without any support materials
yields unordered morphologies (Figure S20). Similar to the growth of g-
CN(0.05) on FTO, the interaction between the –OH groups and the
amine groups leads to a strong g-CN adherence to the glass surface
(Figure S21-S22)), while the one for silicon wafer, Si-N, Si-C, and Si-O
bonds (Figure S23) are responsible for the adherence of g-CN.[19] For
Al/g-CN film, Al-N bond is observable at the interface (Figure S24).[20]
.
The advantage of the large-scale and highly porous g-CN films is
exemplified here by the adsorption of different dyes followed by their
degradation under white light illumination. For that 4 × 4 cm2 g-CN(0)
films were prepared and the adsorption of MB and Rhodamine B (RhB)
was tested (Figure 5c and S31-S33). After 24 h dye uptake, the color of
the g-CN(0) films turned blue and pink, respectively, due to the high dye
adsorption (Figure 5c and Figure S33a), speaking for the strong
interaction between the g-CN and the dyes. The g-CN(x) films exhibit
excellent photocatalytic abilities in the degradation of RhB and MB
under white-light illumination (Figure 5c and Figure S31-S33). After
only 90 seconds, over 95% of RhB was degraded, and the yellowish
color of g-CN(0) film was fully recovered. The complete degradation of
the organic dyes to CO2 was confirmed by analysis of the gaseous
products during illumination (Figure S34). To elucidate the reaction
mechanism, we performed the photodegradation under N2 atmosphere,
air, and with triethanolamine (TEOA) (Figure S31). In the presence of
TEOA, which is commonly used as a hole scavenger, the degradation
rate was dramatically decreased, indicating that the photo-generated
holes are the key species. Similarly, a slower degradation rate was
obtained in the absence of oxygen (under N2 atmosphere) – a known
electron acceptor molecule (Figure S31b, S33(b, d)). Under illumination,
Figure 4. Digital photos of g-CN(0) films with and without 365 nm UV light
illumination on (a) aluminum foil, (b) silicon wafer, (c) glass slide (Letters "PYL"
patterns made of g-CN(0) on glass slide). (d) large sized g-CN(0) film on glass. (e) large
CMBA(0) and g-CN(0) films on FTO.
·
O2 molecules react with the photogenerated electrons to form O2 ,
The strength of this method is demonstrated by the facile patterning
and scalability of the g-CN layer on different substrates. With the aid of
a specific mask (Figure S25), g-CN patterns can be deposited on various
supports (Figure 4c). The present method can be easily applied to large-
scale fabrication of g-CN layers on different substrates, shown here by
the printing of g-CN layer on 6 × 4 cm2 FTO and 8 × 1 cm2 glass slide.
The versatility of this method together with the facile large-scale
fabrication of g-CN layers on different substrates greatly extends the
potential application of g-CN in many field as photo- and electro-
catalysis, light-emitting diodes, solar cells, and heterogeneous catalysis.
To unveil the importance of the supramolecular interaction on the
starting paste synthesis and the resultant g-CN layer, we prepared pastes
solely from each monomer, namely melamine and cyanuric acid.
elongating the life-time of the photo-generated holes, thus, increasing
their probability to react with the dye.[23] The high activity can be also
attributed to the direct contact between the g-CN and the adsorbed dye,
which facilitates the hole transfer from the excited g-CN to the dye. The
g-CN(0) film exhibits better dye degradation ability compared to the
same amount of g-CN(0) powder (Figure S32, S33(c-d)). The enhanced
activity of g-CN film can be attributed to the improved electron-hole
separation stemming from the continuous and thin g-CN structure. The
g-CN films exhibit good stability as demonstrated by two consecutive
photodegradation and dye adsorption recycling tests (Figure 5c). The
unique properties of g-CN films, alongside with the simple and
straightforward fabrication, offers new possibilities for photoelectronic
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10.1002/anie.201711669
Angewandte Chemie International Edition
COMMUNICATION
devices, and catalytic systems such as photocatalysis and self-cleaning
coatings.
within the paste. The g-CN films exhibit high electrochemically
accessible surface area, enhanced photoelectrochemical activity, high
dye adsorption, and excellent dye degradation properties. We believe
that the simplicity, scalability and the precise control of the final g-CN
composition will open many opportunities for the utilization of g-CN in
photocatalysis, electronics, and energy-related applications.
Acknowledgements
We thank Dr. Chabanne for fruitful discussion. M.S thanks the financial
support of the Israel Science Foundation (ISF), grant No. 1161/17. L.X.
thanks the partial support from Guangdong Program for Support of
Distinguished Young Scholar (2017B030306013).
Keywords: graphitic carbon nitride film• supramolecular paste •
doctor blade • porous materials• photocatalysis
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Figure 5. (a) Cathodic and anodic charging currents of g-CN(x) on FTO measured at
0.1 V vs. Ag/AgCl reference electrode as a function of scan rates. The inset shows the
double-layer capacitances values. (b) Roughness factor of the g-CN(x) films. (c) RhB
dye adsorption and photodegradation on g-CN(0) film. (d) SEM image of the g-
CN(0)/g-CN(0.1)/FTO. (e) Photocurrent of the g-CN(0)/g-CN(0.1)/FTO at 1.23 V vs
RHE in 0.1 M KOH.
Electrochemical
impedance
spectroscopy
(EIS)
and
photoelectrochemical (PEC) measurements were used in order to
evaluate the (photo)electrochemical properties of the g-CN(x) on FTO.
EIS results show that the increase of carbon in the final g-CN leads to
higher electronic conductivity (Figure S35a). PEC measurements in 0.1
M KOH reveal that the photocurrent at 1.23 V vs. RHE is doubled for g-
CN(0.1) compared to g-CN(0) (Figure S35b). However, further increase
of the carbon doping leads to a decrease in the photocurrent for g-
CN(0.15), probably due to enhanced recombination, induced by the
carbon sites. Long-term measurement shows that more than 60% of the
initial photocurrent is preserved after 2 h (Figure S36a). SEM images of
the g-CN(0.05) after the stability test indicate that the porous networks
remain intact (Figure S36(b, c)). Another strong merit of this deposition
technique is demonstrated by the facile construction of a heterojunction,
composed from two g-CN layers (g-CN(0)/g-CN(0.1)) with different
bandgaps and energy band positions (Figure 5d). Bandgap diagrams
were determined by the UV-vis spectra and Mott-Schottky
measurements (Figure 2b and S37(a-c)). The heterojunction formation
leads to a strong fluorescence quenching and a prominent increase of the
photocurrent compared to the g-CN(0) and g-CN(0.1) (Figure 5e and
S37d). The improved photoactivity can be explained by the enhanced
charge separation and transportation ensued by the heterojunction
structure (See Figure S37 caption for discussion).
In conclusion, we demonstrated an efficient, simple, and general
method to deposit large-scale, porous g-CN layers on different substrates
using the doctor blade technique. The deposition was made possible by
the synthesis of very uniform supramolecular assembly pastes
comprising only g-CN monomers in ethylene glycol. Theoretical
calculation and experimental data reveal that the paste is formed by a
strong binding of the solvent and the supramolecular assembly. In
addition, the role of the substrates on the g-CN growth was elucidated.
The porosity, thickness, and photophysical properties can be easily
tuned by the tailored design of the starting monomers composition
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Entry for the Table of Contents
COMMUNICATION
An efficient, easy, and general method
for growing highly porous and large-
scale carbon nitride (g-CN) networks
on various substrates using doctor
blade technique is introduced. The g-
CN films exhibit high electrochemical
active surface area, excellent dye
adsorption, good
Guiming Peng, Lidan Xing, Jesús Barrio,
Michael Volokh, and Menny Shalom*
Page No. – Page No.
A General Synthesis of Porous
Carbon Nitride Films with Tunable
Surface Area and Photophysical
Properties
photoelectrochemical and
photodegradation properties. This
facile method opens many
opportunities for the exploitation of g-
CN in electronic and photoelectronic
devices.
This article is protected by copyright. All rights reserved.