Nitrogen Vacancy-Promoted Photocatalytic Activity of Graphitic Carbon Nitride

Niu, Ping; Liu, Gang; Cheng, Hui‐Ming

doi:10.1021/jp301026y

Cited by 601 publications

(406 citation statements)

References 40 publications

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“…Only a few reports have considered the N to C ratio by introducing nitrogen vacancies. [30][31][32] However, most of those cannot lower the valence band of g-C 3 N 4 , because the N replacements are mostly on the linker, -NH x groups, mainly contributing to the n-p* transitions, which are far less active than the p-p* transitions of N in the heptazine units. 9,33,34 A covalent triazine-based framework (CTF-1) is composed of alternating triazine units and phenyl groups in a 12-membered conjugated ring system, as shown in Fig.…”

Section: Introductionmentioning

confidence: 99%

Efficient visible light-driven water oxidation and proton reduction by an ordered covalent triazine-based framework

Xie

Shevlin

Ruan

et al. 2018

Energy Environ. Sci.

244

188

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aWater oxidation is a rate-determining step in solar driven H 2 fuel synthesis and is technically challenging to promote. Despite decades of effort, only a few inorganic catalysts are effective and even fewer are effective under visible light. Recently, attention has been paid to synthetic semiconducting polymers, mainly on graphitic C 3 N 4 , with encouraging hydrogen evolution performance but lower activity for water oxidation. Here, a highly ordered covalent triazine-based framework, CTF-1 (C 8 N 2 H 4 ), is synthesised by a very mild microwave-assisted polymerisation approach. It demonstrates extremely high activity for oxygen evolution under visible light irradiation, leading to an apparent quantum efficiency (AQE) of nearly 4% at 420 nm. Furthermore, the polymer can also efficiently evolve H 2 from water. A high AQE of 6% at 420 nm for H 2 production has also been achieved. The polymer holds great potential for overall water splitting. This exceptional performance is attributed to its well-defined and ordered structure, low carbonisation, and superior band positions. Broader contextSplitting water by sunlight is an attractive renewable approach to generate clean hydrogen for producing chemicals or powering vehicles. This ultra-pure hydrogen also avoids the dreaded catalyst poisoning, which occurs even with very low levels of CO residuals from fossil-fuel generated hydrogen. The key challenge to sustain continued hydrogen generation from this artificial photosynthesis process is to speed up the water oxidation reaction, which is hard to proceed due to multiple electron transfer steps. Oxidation catalysts based on polymeric semiconductors are particularly promising for this purpose because of their abundance leading to low cost, tunable band structure to match the solar spectrum and variable degree of conjugation to impact on the p-p* excitation for efficient electron transfer. With a moderate microwave assisted strategy, we are able to control the degree of conjugation and minimise the undesirable structural carbonisation of a new type of polymeric photocatalyst-covalent triazine-based framework. The optimised catalyst shows advantageous band positions, to capture a wide spectrum of visible light and enhance the charge separation efficiency, leading to very high water oxidation and hydrogen evolution capabilities. The overall discovery paves the way for the development of efficient and continuous clean hydrogen production from the renewable visible-light water splitting process.

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Section: Introductionmentioning

confidence: 99%

Efficient visible light-driven water oxidation and proton reduction by an ordered covalent triazine-based framework

Xie

Shevlin

Ruan

et al. 2018

Energy Environ. Sci.

244

188

View full text Add to dashboard Cite

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“…The increase of d 002 is associated with disordering of the layer structure of GCN due to the presence of residual amino groups in its composition that avoid condensation. Interruption of the structural periodicity of the individual monolayers leads to their deviation from planarity and to increase of d 002 [15]. The material obtained in the present work is characterized by a d 002 value below average, indicating that it is ordered and contains a small number of defects.…”

Section: Resultsmentioning

confidence: 67%

“…The X-ray diffractogram of the product from pyrolysis of urea contains a peak at 27.6°c haracteristic of layered GCN and corresponding to an interlayer distance of d 002 = 0.323 nm [15]. A fairly wide assortment of d 002 values (ranging from 0.319 to 0.326 nm) have been reported for GCN [16][17][18][19][20][21][22], depending on the method of synthesis and on the nature of the initial compound, but in most papers a value of d 002 = 0.326 nm is quoted.…”

Section: Resultsmentioning

confidence: 99%

Nanoparticles of Graphitic Carbon Nitride: Stabilization in Aqueous Solutions, Spectral and Luminescent Properties

et al. 2014

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It was established that stable colloids of graphitic carbon nitride (GCN) can be obtained by relatively mild heat treatment of the bulk material in aqueous solutions of tetraethylammonium hydroxide. The colloids contain particles of average size of 40-45 nm with thicknesses of 6-8 nm. The band gap of the colloidal particles of GCN (3.45 eV) is significantly larger than E g of the bulk material (2.82 eV) as a result of spatial confinement of the charge carriers. The colloidal GCN is characterized by strong photoluminescence emitted in a broad spectral range with a maximum at 410-420 nm and a quantum yield of 21%-22%.Alongside graphene, MoS 2 , and a series of other layered materials graphitic carbon nitride (GCN) C 3 N 4 , which belongs to a class of long known organic polymers [1, 2], has attracted increased attention for researchers in recent years particularly in the region of heterogeneous catalysis and photocatalysis [1][2][3][4][5]. The monolayer of GCN is formed by heptazine heterocycles linked through the tertiary amine nitrogen atom into an infinite one-dimensional aromatic network. Layered GCN, formed by stacking pp interaction between individual monolayers, has semiconducting properties and is characterized by thermostability up to 650-700°C and chemical stability particularly in concentrated acids and alkalis [1,2]. The high stability, the low toxicity, and the fortunate disposition of the permitted energy bands of GCN, giving rise to its sensitivity to visible light and making it possible to realize simultaneously many reduction and oxidation processes involving photogenerated charge carriers, are the prerequisites for the swift development of research into the photocatalytic characteristics of GCN and systems based on it [1-5]. At the same time the effectiveness of many photocatalytic processes involving GCN is limited by its low specific surface area (~10 m 2 /g) on account of the fairly rigorous conditions of production in the course of the pyrolysis of melamine, dicyanodiamide, urea, and other precursors at 500-600°C [1,2]. In this connection searches are being made for methods of template synthesis of mesoporous GCN with a developed surface [3][4][5]. Simultaneously with this approaches are being developed for exfoliation of GCN [6-10] similar to the well-known methods for the exfoliation of graphite and its oxide or the dispersion of bulk GCN to nanosized particles [6,11,12] by extreme heat treatment [6,12] or by the action of oxidizing agents [11]. Such investigations today are sporadic, but the obtained results indicate the existence of a strong relationship between the size of the GCN particles and likewise the number of layers in their composition and the electrophysical and photophysical characteristics of the material [7,10,11,13,14]. This fact gives a special urgency to the search for new methods of dispersion of GCN and stabilization of its nanoparticles in colloidal solutions. The present work was devoted to investigation of the 0040-5760/14/5005-0291

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“…The effects of the increased specific surface area and the usage of a co-catalyst on photocatalytic activity for organic decomposition were investigated. There are many reports on the degradation of organic dyes such as methyl orange and rhodamine B over g-C 3 N 4 [29]. However, the mechanism remains unclear because evaluation using dye may not accurately reflect the catalytic activity under visible-light irradiation [30].…”

Section: Introductionmentioning

confidence: 99%

Improvement of photocatalytic activity of high specific surface area graphitic carbon nitride by loading a co-catalyst

et al. 2014

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Graphitic carbon nitride (g-C 3 N 4 ) was synthesized by heating melamine and was then treated with sodium hydroxide solution under a hydrothermal condition to obtain g-C 3 N 4 with a large specific surface area (HSSA). HSSA shows higher photocatalytic activity for decomposition of acetaldehyde than that of original g-C 3 N 4 . HSSA was modified with RuO 2 as a co-catalyst by the impregnation method. HSSA loaded with 0.05 wt% RuO 2 shows the highest photocatalytic activity for acetaldehyde decomposition under visible light (k = 455 nm).

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Nitrogen Vacancy-Promoted Photocatalytic Activity of Graphitic Carbon Nitride

Cited by 601 publications

References 40 publications

Efficient visible light-driven water oxidation and proton reduction by an ordered covalent triazine-based framework

Efficient visible light-driven water oxidation and proton reduction by an ordered covalent triazine-based framework

Nanoparticles of Graphitic Carbon Nitride: Stabilization in Aqueous Solutions, Spectral and Luminescent Properties

Improvement of photocatalytic activity of high specific surface area graphitic carbon nitride by loading a co-catalyst

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