Porous Carbon Nitride Research Articles

Exploring metal decorated Porphyrin-like Porous Fullerene as catalyst for oxygen reduction reaction: A DFT study

The development of highly active and non-precious catalyst for the oxygen reduction reaction (ORR) at the cathode has been a key challenge for the commercial application of fuel cells in large scale. In this work, we have explored new kind of non-precious catalyst, viz. transition metal decorated porous carbon nitride fullerene (M-C24N24, M = Fe, Co, and Ni) for ORR by using density functional theory as a tool. It was found that these metal atoms, decorated on Porphyrin-like Porous Fullerene, did not tend to aggregate. We have systematically investigated the feasibility of ORR reaction on Fe, Co and Ni-decorated C24N24 systems. To get a primary knowledge about the activity, we have compared the oxygen adsorption energy on these three systems. Then we have calculated the free energies for the intermediate steps to demonstrate the preferred path of oxygen reduction reaction. Interestingly, oxygen reduction reaction is found to proceed through the more efficient four electron reduction path. More interestingly, all the reaction steps are found to be spontaneous on both FeC24N24 and CoC24N24. To draw final conclusion regarding the most efficient catalyst among the three systems, we also analyze the free energy profiles at different electrode potentials.

Preparation, Physicochemical Properties, and Functional Characteristics of Carbon Nitride: a Review

Data on the methods of preparation, structure, physicochemical properties, and functional characteristics of carbon nitride have been summarized and analyzed. Promise for the use of porous carbon nitride of various stoichiometries in photocatalysis, catalysis, and adsorption has been noted. Some general observations about the state and possible directions for the development of research in this field of physical chemistry were given.

Large Scale Synthesis of Porous Carbon-Nitride Microsphere for Visible Light Harvesting

Porous carbon nitride microsphere with dimaters ranging from 2 to 6 micrometers were synthesized via chemical vapor deposition in this work. Electron microscope images of the composite show that they have multiwalled innerstructure, which was built by disorderly stacked g-C3N4 curved layers assembled from nitrogen bridges of pyramidal structure, making them porous surfaced. Their mechanical and optical properties were studied with nanoindenter and UV-VIS spectra. It shows that they have good mechanical properties and, compared to carbon nitride synthesized by solvent method, out carbon nitride composite showed relativly broader light absorption band between 400 nm and 600 nm. Also, its visible light degradation of methyl blue was studied, showing its potential as visible light photocatalytic for water purification.

Insight into highly efficient simultaneous photocatalytic removal of Cr(VI) and 2,4-diclorophenol under visible light irradiation by phosphorus doped porous ultrathin g-C3N4 nanosheets from aqueous media: Performance and reaction mechanism

Carbon nitride (g-C3N4) has attracted great attention for its wide applications in hydrogen evolution and photocatalytic degradation. In this study, phosphorus doped porous ultrathin carbon nitride nanosheets (PCN-S) were prepared successfully via the element doping and thermal exfoliation method. The prepared PCN-S was characterized by XRD, SEM, TEM, N2-adsorption-desorption measurement, FT-IR, XPS, UV–vis diffuse reflectance spectra, photoluminescence (PL), photocurrent response (I-t) and EIS. The results show that PCN-S owns regular crystal structure of g-C3N4, large specific surface areas and nanosheet structure with lots of in-plane pores on its surface, excellent chemical stability, and broad light response to the whole visible light region, which was attributed to the doping of phosphorus element. Under visible light irradiation, the photocatalytic reduction of Cr(VI) over different samples indicated that the P doping and porous nanosheet structure play an important role for the enhanced performance of PCN-S. The reason was that P element doping can broaden the visible light response region, and large specific surface areas from the porous nanosheet structure can provide quantities of active sites for the photocatalytic reaction. Then the detailed study on the PCN-S for simultaneous photocatalytic reduction of Cr(VI) and oxidation of 2,4-diclorophenol (2,4-DCP) was conducted. The experiments results show that low pH value and enough dissolved oxygen were found to promote Cr(VI) reduction and 2,4-DCP oxidation. The detailed photocatalytic mechanism was proposed. The strategies used in this study could provide new insight into the design of g-C3N4 based materials with high photocatalytic activity, and present potential for the treatment of Cr(VI)/2,4-DCP or other mixed pollutants in wastewater.

Simple method for preparing of sulfur–doped graphitic carbon nitride with superior activity in CO2 photoreduction

AbstractS‐doped porous carbon nitride was obtained by a simple method using melamine and sulfuric acid. The synthesized material exhibits high BET specific surface area (75 m2/g) compared to non‐doped C3N4 (25 m2/g). According to X‐ray photoelectron spectroscopy sulfur atoms substitute nitrogen forming C−S bonds in the structure of carbon nitride. Incorporation of sulfur into C3N4 results in a significant increase of the light absorbance intensity especially in the UV region compared to undoped sample. Synthesized S‐doped carbon nitride was found to be p‐type semiconductor with high catalytic activity towards photoreduction of carbon dioxide with water vapour. Doping C3N4 with sulfur increases the catalytic activity in this reaction almost tenfold.

Acetic acid induced synthesis of laminated activated carbon nitride nanostructures

Graphitic carbon nitride (g-C3N4), composed of only non-metallic elements, possesses a graphene-like structure and an appropriate band gap around 2.7 eV. It is finding its promising applications in sustainable chemistry. In this paper, highly ordered laminated porous carbon nitride nanostructures (OLP-C3N4) are successfully prepared via a novel two-step hydrothermal-calcination method using acetic acid as the order-inducing agent and pore-forming agent. Acetic acid and melamine are first hydrothermally synthesized to form a solid precursor. Then, the precursor is calcinated to obtain the product. The electrostatic interaction existed between acetic acid and melamine in water during the hydrothermal process is considered to play a key role on the formation of layered nanostructures. While, carboxyl group in acetic acid is favorable for the porous structure of the products. The prepared carbon nitride nanostructures exhibit high surface area and show excellent electric transport and optical properties, which may have wide applications in catalytic, adsorptive and battery materials fields. This work opens a novel way for the preparing hierarchical porous materials with unique properties.

Strongly Coupled Ternary Hybrid Aerogels of N-deficient Porous Graphitic-C3N4 Nanosheets/N-Doped Graphene/NiFe-Layered Double Hydroxide for Solar-Driven Photoelectrochemical Water Oxidation.

Developing photoanodes with efficient sunlight harvesting, excellent charge separation and transfer, and fast surface reaction kinetics remains a key challenge in photoelectrochemical water splitting devices. Here we report a new strongly coupled ternary hybrid aerogel that is designed and constructed by in situ assembly of N-deficient porous carbon nitride nanosheets and NiFe-layered double hydroxide into a 3D N-doped graphene framework architecture using a facile hydrothermal method. Such a 3D hierarchical structure combines several advantageous features, including effective light-trapping, multidimensional electron transport pathways, short charge transport time and distance, strong coupling effect, and improved surface reaction kinetics. Benefiting from the desirable nanostructure, the ternary hybrid aerogels exhibited remarkable photoelectrochemical performance for water oxidation. Results included a record-high photocurrent density that reached 162.3 μA cm(-2) at 1.4 V versus the reversible hydrogen electrode with a maximum incident photon-to-current efficiency of 2.5% at 350 nm under AM 1.5G irradiation, and remarkable photostability. The work represents a significant step toward the development of novel 3D aerogel-based photoanodes for solar water splitting.

Water-assisted ions in situ intercalation for porous polymeric graphitic carbon nitride nanosheets with superior photocatalytic hydrogen evolution performance

Two-dimension layered polymeric carbon nitride possessing unique electronic structure and high specific surface area exhibits immense potentials for visible light driven photocatalytic activity for hydrogen production by the decomposition of water molecules. Herein, porous polymeric carbon nitride nanosheets were obtained by lithium chloride ions in situ intercalating bulk materials in thermal polycondensation process and followed by liquid exfoliation in water. The porous nanosheets show two-dimension layered structure with the thickness of 2–3nm, a high density in-plane pores with 2–3nm diameter, a higher surface area (186.3m2g−1), enlarged bandgap (by 0.16eV), prolonged charge carrier lifetime, enhanced electronic transport ability, increased charge carrier density and improved photocurrent responses, which could significantly give rise to photocatalytic activity. The results highlight the crucial role of 2D porous structure, high specific surface area and unique electronic structure on the photocatalytic performance of polymeric carbon nitride materials.

Highly Efficient Quantum Sieving in Porous Graphene-like Carbon Nitride for Light Isotopes Separation.

Light isotopes separation, such as 3He/4He, H2/D2, H2/T2, etc., is crucial for various advanced technologies including isotope labeling, nuclear weapons, cryogenics and power generation. However, their nearly identical chemical properties made the separation challenging. The low productivity of the present isotopes separation approaches hinders the relevant applications. An efficient membrane with high performance for isotopes separation is quite appealing. Based on first-principles calculations, we theoretically demonstrated that highly efficient light isotopes separation, such as 3He/4He, can be reached in a porous graphene-like carbon nitride material via quantum sieving effect. Under moderate tensile strain, the quantum sieving of the carbon nitride membrane can be effectively tuned in a continuous way, leading to a temperature window with high 3He/4He selectivity and permeance acceptable for efficient isotopes harvest in industrial application. This mechanism also holds for separation of other light isotopes, such as H2/D2, H2/T2. Such tunable quantum sieving opens a promising avenue for light isotopes separation for industrial application.

Highly efficient simulated solar-light photocatalytic oxidation of gaseous NO with porous carbon nitride from copolymerization with thymine and mechanistic analysis

We synthesized novel and efficient porous carbon nitride (CN) photocatalysts by facial supramolecular approach using cyanuric acid (C), melamine (M) and thymine (T) as starting material. The T-modified CNs display excellent photophysical and photochemical properties: high specific surface area, strong light adsorption as well as low recombination rate of photoinduced electron–hole pairs. They exhibit tremendous enhanced photocatalytic activity on photocatalytic oxidation (PCO) of NO (∼400 ppm) under simulated solar-light irradiation, wherein the CM + 2.5 mol%-T possesses the highest photoactivity (93.3% in 40 min). The enhanced photocatalytic performance is ascribed to the synergic effect of large specific surface area and high separation and transfer efficiency of photoinduced electron–hole pairs. In the PCO of NO process, the main reaction product is NO3−, which was confirmed by Ion Chromatography. In addition, the mechanism of PCO is also intuitively analyzed by trapping experiment. The results indicate that ˙O2− plays a leading role in the PCO of NO process.

Electron acceptor of Ni decorated porous carbon nitride applied in photocatalytic hydrogen production.

Nickel, a non-noble metal, is one of the most promising candidates for photocatalysis because it is inexpensive and an earth-abundant metal. Herein, Ni/CM-C3N4 nanocomposites with Ni as a cocatalyst were synthesized by a simple solvothermal method. Field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) confirmed that Ni nanoparticles were loaded onto the surface of CM-C3N4. The prepared Ni/CM-C3N4 nanocomposites exhibited an enhanced hydrogen evolution activity. The most active catalyst contained 10% Ni and produced H2 at a rate of 313.2 μmol h-1 g-1, which was obviously higher than that of pure CM-C3N4. The results of photoluminescence (PL) and photoacoustics (PA) studies indicated that the recombination efficiency of photo-induced electron-hole pairs was decreased for CM-Ni10 as compared to that for unmodified CM-C3N4. The transient photovoltage (TPV) measurements directly demonstrated that the recombination time of electron-hole pairs in CM-Ni10 was prolonged. More importantly, the reversed surface photovoltage (SPV) and the declined surface photocurrent (SPC) response of CM-Ni10 revealed that the photogenerated electrons could be trapped by Ni, leading to a better separation efficiency and a superior hydrogen production. Finally, the possible mechanism is proposed to illuminate the photogenerated charge behavior between CM-C3N4 and Ni, which might provide a theoretical basis to develop efficient cocatalysts for photocatalytic water splitting.

Hollow porous carbon nitride immobilized on carbonized nanofibers for highly efficient visible light photocatalytic removal of NO.

With the deterioration of air quality, great efforts were devoted to designing various photocatalysts for effective removal of NOx in air. However, the present photocatalysts have a fatal problem of low photocatalytic efficiency. In this work, a hollow porous carbon nitride nanosphere coupled with reduced graphene oxide (HCNS/rGO) was exploited as a visible-light photocatalyst to remove nitrogen monoxide in air at a low concentration (600 ppb level) under irradiation of an energy saving lamp. HCNS/rGO showed a NO removal ratio of 64%, which was superior to that of most other visible-light photocatalysts. The excellent photocatalytic ability of HCNS/rGO originates from the hollow porous morphology of HCNS and the grafted rGO on the surface. HCNS/rGO was immobilized on porous carbonized polymer nanofibers to obtain a photocatalytic membrane without affecting photocatalytic efficiency. Furthermore, the membrane showed excellent photochemical stability and recyclability.

Hard template synthesis of porous carbon nitride materials with improved efficiency for photocatalytic CO2 utilization

Abstract Porous carbon nitrides of different morphology were obtained via bulk and hard template (SBA-15 and MCF) pyrolysis of melamine. Matrix method allowed obtaining ordered porous C 3 N 4 with higher bandgap (2.87 eV) in the contrary to the bulk sample (2.45 eV). Obtained carbon nitrides were found to be p-type semiconductors with catalytic activity towards photoreduction of carbon dioxide with water vapour. Carbon nitride obtained in MCF has the higher bandgap, developed surface, sponge-like morphology, spatially ordering and it's characterized by the highest photocatalytic activity.

Selective and Regenerative Carbon Dioxide Capture by Highly Polarizing Porous Carbon Nitride.

Energy-efficient CO2 capture is a stringent demand for green and sustainable energy supply. Strong adsorption is desirable for high capacity and selective capture at ambient conditions but unfavorable for regeneration of adsorbents by a simple pressure control process. Here we present highly regenerative and selective CO2 capture by carbon nitride functionalized porous reduced graphene oxide aerogel surface. The resultant structure demonstrates large CO2 adsorption capacity at ambient conditions (0.43 mmol·g(-1)) and high CO2 selectivity against N2 yet retains regenerability to desorb 98% CO2 by simple pressure swing. First-principles thermodynamics calculations revealed that microporous edges of graphitic carbon nitride offer the optimal CO2 adsorption by induced dipole interaction and allows excellent CO2 selectivity as well as facile regenerability. This work identifies a customized route to reversible gas capture using metal-free, two-dimensional carbonaceous materials, which can be extended to other useful applications.

Facile synthesis of porous graphene-like carbon nitride (C6N9H3) with excellent photocatalytic activity for NO removal

We reported the possible synthesis of a new porous graphene-like carbon nitride (C6N9H3) by simply adding hydrochloric acid in the precursor of block g-C3N4. The formation of the porous graphene-like C6N9H3 can be attributed to the change in the thermal condensation modal of the precursor and the acidic condition induced by Cl− and H+. The photocatalytic activity of the samples was evaluated by the removal of NO under visible light illumination. We found that the porous graphene-like C6N9H3 exhibited enhanced photocatalytic activity compared to the block g-C3N4. We also researched the removal mechanism and found that the removal of NO in our systems was due to the synergic effect of h+ and O2−. This study could shed light on the design of efficient photocatalysts and facilitate a deep understanding of the NO removal mechanism through photocatalytic technology.

Synthesis and comparative study of the photocatalytic performance of hierarchically porous polymeric carbon nitrides

Graphitic carbon nitride materials with tri-s-triazine and s-triazine based structures were prepared by thermal condensation of melamine (CNT) and by solution reaction of cyanuric chloride with lithium nitride (CNS), respectively. An amphiphilic block copolymer-F68 was used as a soft template for the synthesis of mesoporous carbon nitride. The structural and photophysical properties of the as-prepared catalysts were characterized by X-ray powder diffraction, elemental analysis, N2-adsorption measurement, transmission electron microscopy, X-ray photoelectron spectroscopy, differential scanning calorimeter and UV–Vis absorption as well as time-resolved picosecond emission spectroscopy. The photocatalytic activity of the samples was evaluated by H2 evolution from water under visible light irradiation and the degradation of rose bengal (RB). The mesoporous CNT materials prepared with Pluronic F68 as template showed markedly higher activity compared to bulk carbon nitride, which can be attributed to its crystallinity, hierarchical porous structure and the enlarged surface area. The catalyst was relatively stable as proven by recycling experiments. Besides, the addition of H2O2 promoted the formation of active ·OH radicals and increased the activity of carbon nitride for photodegradation of rose bengal. The carbon nitrides prepared by solution reactions were of very poor activity both in photocatalytic water splitting and rose bengal degradation.

Environment-friendly preparation of porous graphite-phase polymeric carbon nitride using calcium carbonate as templates, and enhanced photoelectrochemical activity

Superior to silica nanoparticles, the easily accessible and removable CaCO3 particles produced porous carbon nitride with photocurrents 7.5-times that of the bulk one.

Efficient and Durable Visible Light Photocatalytic Performance of Porous Carbon Nitride Nanosheets for Air Purification

Graphitic carbon nitride (g-C3N4) is an intriguing metal-free photocatalyst for pollution control. This research represents an efficient visible light photocatalytic removal of gaseous NO at 600 ppb level with porous g-C3N4 nanostructures synthesized by pyrolysis of thiourea. TG-DSC was employed to simulate the pyrolysis of thiourea, and the mechanistic formation process of g-C3N4 was revealed. The crystallinity, morphology, surface area, pore structures, band structure, and photocatalytic activity of g-C3N4 can be engineered by variation of pyrolysis temperature and time. A layer-by-layer coupled with layer-splitting process was proposed for the gradual reduction of layer thickness and size of g-C3N4 obtained at elevated temperature and prolonged time. The visible light photocatalytic activity of g-C3N4 nanosheets toward NO purification was significantly enhanced due to the enhanced crystallinity, nanosheet structure, large surface areas and pore volume and enlarged band gap as the pyrolysis temperature ...

Porous carbon nitride nanosheets for enhanced photocatalytic activities.

Porous carbon nitride nanosheets (PCNs) have been prepared for the first time by a simple liquid exfoliation method via probe sonication. These mesoporous nanosheets of around 5 nm in thickness combine several advantages including high surface area, enhanced light absorption and excellent water dispersity. It can be used as a versatile support for co-catalyst loading for photocatalytic dye degradation and water reduction. With 3.8 wt% Co(3)O(4) loaded, PCNs can achieve more efficient photocatalytic degradation of Rhodamine B, compared with non-porous C(3)N(4) nanosheets (CNs), bulk porous C(3)N(4) (PCN) and bulk nonporous C(3)N(4) (CN). With 1.0 wt% Pt loaded, CNs and PCN exhibit 7-8 times enhancement in H2 evolution than CN. Remarkably, PCNs with both porous and nanosheet-like features achieve 26 times higher activity in H2 evolution than CN. These significant improvements in photocatalytic activities can be attributed to the high surface area as well as better electron mobility of the two-dimensional nanostructure.

Template-free Synthesis of Highly Porous Carbon Nitride, nanoC3N4

Abstract A novel template-free and postsynthetic preparation of a highly porous carbon nitride material, nanoC3N4, was developed using concentrated sulfuric acid as the dispersion medium, followed by impregnation with ethanol. nanoC3N4 has a structure similar to that of graphitic carbon nitride composed of melem polymers but has a stronger basicity.