Graphitic Carbon Nitride Nanotubes Research Articles

Thermal Conductivity of Graphitic Carbon Nitride Nanotubes: A Molecular Dynamics Study

Graphitic carbon nitride (g-C3N4) nanotubes are recently gaining increasing interest due to their extraordinary physicochemical properties. In the following, we report on simulations using a method of nonequilibrium molecular dynamics and focus on the thermal conductivity variation of g-C3N4 nanotubes with respect to different temperatures, diameters, and chiral angles. In spite of the variation of diameters and chiral angles, the structure of nanotubes possesses high stability in the temperature range from 200 K to 600 K. Although there is little change of the thermal conductivity per unit arc length for nanotubes with the same diameter at different temperatures, it decreases significantly with increasing diameters at the same temperature. The thermal conductivity at different chiral angles has little to do with how temperature changes. Simulation results show that the vibrational density of states of nanotubes distributed, respectively, at ∼11 THz and ∼32 THz, indicating that heat in nanotubes is mostly carried by phonons with frequencies lower than 10 THz.

Ordered and Ultralong Graphitic Carbon Nitride Nanotubes Obtained via In-Air CVD for Enhanced Photocatalytic Hydrogen Evolution

Ordered and Ultralong Graphitic Carbon Nitride Nanotubes Obtained via In-Air CVD for Enhanced Photocatalytic Hydrogen Evolution

A Photoelectrochemical Aptasensor for Acetamiprid Determination Based on λ Exonuclease-Assisted Recycling Amplification and DNAzyme-Catalyzed Precipitation

In the present work, we developed a selective and sensitive photoelectrochemical (PEC) aptasensor for acetamiprid determination. Due to specific recognition ability of the aptamer, acetamiprid could combine with its aptamer, leading to the release of the primer from the aptamer-primer hybrid duplex and the formation of 5′-phosphorylated double-stranded DNAs on the nanocomposite of graphitic carbon nitride and titanium dioxide nanotube array (TNA/g-C3N4), which could be catalytically recycling-digested by λ exonuclease, leading to the amplification of the signal, and the generated DNAzymes could catalyze the in situ production of benzo-4-chlorohexadienone (4-CD) precipitate in the presence of H2O2, causing the significant decrease of photocurrent response of TNA/g-C3N4. Under the optimal experimental conditions, the logarithm of decrease value of photocurrent was linear proportional to the logarithm of acetamiprid concentration from 0.1 pM to 1.0 nM. And the constructed PEC aptasensor exhibited a low limit of detection (0.025 pM) and good selectivity towards acetamiprid determination, which has been successfully applied for the analysis of real vegetable samples with good precision of RSD less than 4.3% and good accuracy of the recoveries ranged from 96.4% to 104.3%.

Development of a novel graphitic carbon nitride and multiwall carbon nanotube co-doped Ti/PbO2 anode for electrocatalytic degradation of acetaminophen

In this work, we have constructed a novel graphitic carbon nitride/multiwall carbon nanotube (GCN/CNT) doped Ti/PbO2 as anode for highly effective degradation of acetaminophen (ACE) wastewater. The ACE removal efficiency of 83.2% and chemical oxygen demand removal efficiency of 76.3% are achieved under the optimal condition of temperature 25 °C, initial pH 7, current density 15 mA cm−2 and Na2SO4 concentration 6.0 g L−1. The excellent electrocatalytic activity of Ti/PbO2-GCN-CNT anode for ACE oxidation is ascribed to the effective suppression of oxygen evolution and the enhanced electron transfer after introducing GCN and CNT. Furthermore, Ti/PbO2-GCN-CNT electrode displays excellent stability and reusability. ACE degradation is accomplished by direct oxidation and indirect oxidation, and ∙OH radical plays primary role in the indirect oxidation of ACE wastewater. The intermediates of ACE degradation are detailly investigated using LC-MS analysis and a possible degradation mechanism is proposed.

Nitrogen‐Deficient Graphitic Carbon Nitride/Carbon Nanotube as Polysulfide Barrier of High‐Performance Lithium‐Sulfur Batteries

AbstractLithium‐sulfur (Li−S) batteries have been attracting growing interest in the past few years due to their outstanding theoretical energy density, but the lower cycle performance and especially the migration of polysulfides significantly inhibited its applicability. Herein, we propose a novel strategy for trapping lithium polysulfides (LiPSs) by combining nitrogen‐deficient graphitic carbon nitride (g‐C3N4–x) and carbon nanotubes (CNTs) to form a functional interlayer between the separator and sulfur cathode in Li−S batteries. The defect chemistry present in g‐C3N4–x not only improves the chemical affinity toward polysulfides but also catalyzes the polysulfide reactions. Besides, the interwoven scaffold‐like CNT network in the g‐C3N4–x/CNT composite accelerates the process of electron transfer. Based on this synergistic effect, the cells with g‐C3N4–x/CNT‐modified separators showed a remarkable discharge capacity of 1128 mAh g−1 at 0.2 C, and a reversible capacity of 774 mAh g−1 after 100 cycles, indicating an efficient strategy toward high‐performance modified separators.

Self-assembled synthesis of oxygen-doped g-C3N4 nanotubes in enhancement of visible-light photocatalytic hydrogen

Abstract Currently, photocatalytic water splitting is regarded as promising technology in renewable energy generation. However, the conversion efficiency suffers great restriction due to the rapid recombination of charge carriers. Rational designed the structure and doping elements become important alternative routes to improve the performance of photocatalyst. In this work, we rational designed oxygen-doped graphitic carbon nitride (OCN) nanotubes derived from supermolecular intermediates for photocatalytic water splitting. The as prepared OCN nanotubes exhibit an outstanding hydrogen evolution rate of 73.84 μmol h−1, outperforming the most of reported one dimensional (1D) g-C3N4 previously. Due to the rational oxygen doping, the band structure of g-C3N4 is meliorated, which can narrow the band gap and reduce the recombination rate of photogenerated carriers. Furthermore, the hollow nanotube structure of OCN also provide multiple diffuse reflection during photocatalytic reaction, which can significantly promote the utilization capacity of visible light and enhance the photocatalytic water splitting performance. It is believed that our work not only rationally controls the nanostructure, but also introduces useful heteroatom into the matrix of photocatalyst, which provides an effective way to design high-efficiency g-C3N4 photocatalyst.

Construction of three-dimensional g-C3N4/Gr-CNTs/TiO2 Z-scheme catalyst with enhanced photocatalytic activity

A three-dimensional (3D) photocatalyst was synthesized through the self-assembly of graphitic carbon nitride (g-C3N4), TiO2, graphene (Gr), and carbon nanotubes (CNTs), in which both Gr and CNTs act as electron mediators, to form an all-solid-state g-C3N4/Gr-CNTs/TiO2 Z-scheme photocatalytic system. In this Z-scheme photocatalyst, the highly interconnected CNTs not only can effectively promote the transfer of photogenerated charge carriers, but also built a 3D open frame network to harvest more incident light and provide more specific surface area for photoreactions. Benefiting from the 3D nanostructure and Z-scheme system, phenol removal over g-C3N4/Gr-CNTs/TiO2 reached up to 90% within 120 min using a high-pressure Xe short-arc lamp as light source, which was much higher than that achieved over pure g-C3N4. The 3D Z-scheme photocatalyst fabricated in this study may be an attractive material for many environmental and energy-related applications.

Graphitic carbon nitride nanotubes: a new material for emerging applications.

We provide a critical review of the current state of the synthesis and applications of nano- and micro-tubes of layered graphitic carbon nitride. This emerging material has a huge potential for light-harvesting applications, including light sensing, artificial photosynthesis, selective photocatalysis, hydrogen storage, light-induced motion, membrane technologies, and can become a major competitor for such established materials as carbon and titania dioxide nanotubes. Graphitic carbon nitride tubes (GCNTs) combine visible-light sensitivity, high charge carrier mobility, and exceptional chemical/photochemical stability, imparting this material with unrivaled photocatalytic activities in photosynthetic processes, such as water splitting and carbon dioxide reduction. The unique geometric GCNT structure and versatility of possible chemical modifications allow new photocatalytic applications of GCNTs to be envisaged including selective photocatalysts of multi-electron processes as well as light-induced and light-directed motion of GCNT-based microswimmers. Closely-packed arrays of aligned GCNTs show great promise as multifunctional membrane materials for the light energy conversion and storage, light-driven pumping of liquids, selective adsorption, and electrochemical applications. These emerging applications require synthetic routes to GCNTs with highly controlled morphological parameters and composition to be available. We recognize three major strategies for the GCNT synthesis including templating, supramolecular assembling of precursors, and scrolling of nano-/microsheets, and outline promising routes for further progress of these approaches in the light of the most important emerging applications of GCNTs.

Large-Scale Preparation of g-C3N4 Porous Nanotubes with Enhanced Photocatalytic Activity by Using Salicylic Acid and Melamine

Graphitic carbon nitride (g-C3N4) nanotubes were produced by using salicylic acid-mediated melamine successfully. The obtained long g-C3N4 nanotube possesses a large specific surface area and a par...

High-performance thin film nanocomposite membranes enabled by nanomaterials with different dimensions for nanofiltration

The incorporation of nanomaterials into a polyamide (PA) matrix has been demonstrated to be effective in the design of advanced thin film nanocomposite (TFN) membranes. In this study, a novel TFN membrane was developed by simultaneous introduction of two nanofillers with different dimensions. Graphitic carbon nitride (g-C3N4) and halloysite nanotubes (HNTs) were co-deposited onto a substrate surface with piperazine (PIP) monomers via vacuum filtration, followed by interfacial polymerization (IP) with trimesoyl chloride (TMC). A series of characterizations showed that the pre-loaded g-C3N4 was present as nanoaggregates wrapped by the formed PA film, while one-dimensional HNTs inclined to be horizontally aligned as a hydrophilic interlayer. This unique architecture led to a crumpled membrane surface with convex and ridged structures, and provided additional water transport channels. The surface roughness and hydrophilicity of the TFN membranes were also enhanced with the addition of nanomaterials. Although g-C3N4 and HNTs were able to elevate the water permeance, a superior separation performance could only be achieved by simultaneously incorporating these two nanofillers. The best performing TFN membrane containing 16.4 μg cm−2 g-C3N4 and 19.7 μg cm−2 HNTs exhibited a water permeance of 20.5 L m−2 h−1 bar−1, nearly twice as high as that of the thin film composite (TFC) membrane, while maintaining a comparably high Na2SO4 rejection of 94.5%. This demonstrated the effectiveness of g-C3N4 and HNTs in developing high-performance TFN membranes, which were ascribed to their respective advantages as well as the combined effect in the regulation of the PA layer microstructure.

Nitrogen-rich graphitic carbon nitride nanotubes for photocatalytic hydrogen evolution with simultaneous contaminant degradation

Graphitic carbon nitride (g-C3N4) has aroused great concern since it applied to the photocatalytic process. However, the inherent shortcomings of bulk g-C3N4, such as small active surface area, low separation efficiency of photogenerated carriers, sluggish charge transport process, etc., result in low-level photocatalytic performance. The rich-nitrogen carbon nitride nanotubes (CNNTs) made by an easy supermolecule self-assembly method could slove these subsisting problems. The CNNTs with unique morphology possess superior separation/migration of photo-excited charge carriers and enhanced photocatalytic performance. Under irradiation with visible light (λ > 400 nm), measured with Pt (3 wt%) as co-catalyst, the CNNTs have a hydrogen evolution rate of 18.06 mmol h−1 g−1 and its apparent quantum yield (AQY) is 12.55% (420 nm). The CNNTs are also applied to degrade antibiotics with simultaneous hydrogen production, providing a method for alleviating energy crisis and environmental pollution issues. The degradation rate of bisphenol A (BPA) is 92% and simultaneously with 13.63 μmol photocatalytic hydrogen generation after irradiation for 5 h.

Template free synthesis of graphitic carbon nitride nanotubes mediated by lanthanum (La/g-CNT) for selective photocatalytic CO2 reduction via dry reforming of methane (DRM) to fuels

Template-free fabrication of graphitic carbon nitride nanotubes modified with lanthanum (La/g-CNT) for dynamic photo-catalytic CO2 reduction with CH4 has been investigated. Successful fabrication of g-C3N4 nanosheets and nanotubes were obtained with enhanced photo-activity under visible-light. Using 5 wt% La/g-CNT, CO yield of 491 µmole g-cat−1 h−1 was obtained which is 3.6 and 5.9 folds higher than g-CNS and g-CN samples. Similarly, production of H2 was highest over La/g-CNT which was 2.95 folds more than g-CNT and 5.1 times higher than using g-CN. Although, pristine g-CN has more basic sites and larger BET surface area but enhanced photo-activity over La/g-CNT can be attributed to efficient transfer of electrons over 1D structure and separation of charge carriers by La. More interestingly, effect of CH4/CO2 feed ratios was obvious, whereas, highest CO was produced at CH4/CO2 ratio of 1.0 but H2 was maximum with ratio of 2.0. Among the different reaction systems, highest CO was obtained using DRM, while CO2 reduction by H2/H2O promoted both CO and CH4 production. This was obviously due to basic characteristics, sorption competition over the catalyst surface and favorable reverse water gas shift (RWSG) reaction. The stability test further confirmed the suitability of this material which prevailed until three cycles without obvious deactivation. This work will open new opportunities to develop structured nanocalaysts for solar energy based reutilization of CO2 and CH4 for the production of renewable fuels.

Porous nitrogen-rich g-C3N4 nanotubes for efficient photocatalytic CO2 reduction

The conversion of carbon dioxide (CO2) into fuels and valuable chemicals using solar energy is a promising method for reducing CO2 emissions and solving energy supply issues. However, the development of inexpensive, efficient and metal-free materials for photocatalytic CO2 reduction is challenging. Herein, we report a facile supramolecular self-assembly strategy for the preparation of porous nitrogen-rich graphitic carbon nitride (g-C3N4) nanotubes with Lewis basicity and a large surface area, which are beneficial for the adsorption of CO2 and, consequently, the enhancement of the photocatalytic CO2 reduction activity. The metal-free porous nitrogen-rich g-C3N4 nanotubes catalyst exhibits a superior visible-light-induced CO2-to-CO conversion rate of 103.6 μmol g−1 h−1, which is 17 and 15 times higher than those of bulk g-C3N4 (6.1 μmol g−1 h−1) and P25-TiO2 (7.1 μmol g−1 h−1), respectively, and exceeds the performance of most metal-free photocatalysts. This work provides new insights into the synthesis of functional groups-modified g-C3N4 with a unique structure for effective photocatalytic CO2 reduction.

NiCo alloy nanoparticles encapsulated in multi-dimensional N-doped carbon architecture as efficient bifunctional catalyst for rechargeable zinc-air batteries

One of the crucial issues in rechargeable zinc-air batteries is to explore low-cost, highly efficient bifunctional electrocatalysts for the oxygen reduction/evolution reaction. Here, the unique NiCo alloy nanoparticles encapsulated in the multi-dimensional nitrogen-doped carbon architecture (NiCo/MNC) is reported as an effective bifunctional catalyst for rechargeable zinc-air batteries. The multi-dimensional nitrogen-doped carbon architecture was synthesized through the rapid calcination of two-dimensional graphitic carbon nitride (g-C3N4) and one-dimensional multi-walled carbon nanotubes (MWCNTs). The g-C3N4 serves as the nitrogen source and the precursor for N-doped carbon nanosheets (NCSs). Simultaneously, NCSs can intertwine with MWCNTs to further obtain the multi-dimensional architecture with a large specific surface area. The synergistic effect between multi-dimensional nitrogen-doped carbon architectures and NiCo alloy nanoparticles endowed the NiCo/MNC with a positive half-wave potential of 0.83 V (vs. RHE: Reversible Hydrogen Electrode) for oxygen reduction reaction and a low potential of 1.61 V (vs. RHE) at the current density of 10 mA cm−2 for oxygen evolution reaction. Moreover, the zinc-air battery assembled with NiCo/MNC as the air-cathode exhibited a high-power density of 135.2 mW cm−2, a specific capacity of 701.7 mAh g−1, and an excellent stability in charging/discharging cycle test (over 115 h). The prepared catalyst could potentially serve to take the place of precious metal catalysts in rechargeable zinc-air batteries.

Supramolecular precursor strategy for the synthesis of holey graphitic carbon nitride nanotubes with enhanced photocatalytic hydrogen evolution performance

A simple one-step thermal polymerization method was developed for synthesis of holey graphitic carbon nitride nanotubes, involving direct heating of mixtures of melamine and urea or melamine and cyanuric acid in specific mass ratios. Supramolecular structures formed between the precursor molecules guided nanotube formation. The porous and nanotubular structure of the nanotubes facilitated efficient charge carrier migration and separation, thereby enhancing photocatalytic H2 production in 20 vol.% lactic acid under visible light irradiation. Nanotubes synthesized using melamine and urea in a 1:10 mass ratio (denoted herein as CN-MU nanotubes) exhibited a photocatalytic hydrogen production rate of 1,073.6 μmol·h−1·g−1 with Pt as the cocatalyst, a rate of 4.7 and 3.1 times higher than traditional Pt/g-C3N4 photocatalysts prepared from graphitic carbon nitride (g-C3N4) obtained by direct thermal polymerization of melamine or urea, respectively. On the basis of their outstanding performance for photocatalytic H2 production, it is envisaged that the holey g-C3N4 nanotubes will find widespread uptake in other areas, including photocatalytic CO2 reduction, dye-sensitized solar cells and photoelectrochemical sensors.

Ag-La loaded protonated carbon nitrides nanotubes (pCNNT) with improved charge separation in a monolithic honeycomb photoreactor for enhanced bireforming of methane (BRM) to fuels

Well-designed Ag-La modified protonated graphitic carbon nitride nanotubes (pCNNT) are fabricated via a template-free sonicated assisted one-pot hydrothermal method. The structure and properties of the catalyst samples are obtained by XRD, SEM, TEM, EDX, N2-sorption, XPS, UV–vis DRS and PL spectroscopy characterization techniques. The effect of Ag-La-modified pCNNT is evaluated for different CH4 reforming processes such as dry reforming of methane (DRM) and bi-reforming of methane (BRM), carried out in a fixed-bed and monolithic honeycomb photoreactor systems under UV and visible light irradiations. The optimized 3%Ag-5%La/pCNNT performance displayed increased productivity under UV-light due to more production of charges with strong ability for cleaving both stable CO2 and CH4 molecules. More importantly, the performance of Ag-La loaded pCNNT is 1.45 and 2.10 folds higher for CO and H2 production, respectively compared with Ag-La loaded pCN nanosheets. CO and H2 evolutions prevailed in a monolith photoreactor compared to fixed-bed reactor. Besides, the amount of CO, H2 and CH3OH are 1.79, 2.12 and 2.13 folds higher in BRM compared to DRM. The improved performance can be ascribed to effective interfacial carrier separation due to Ag-La synergistic effect with suitable redox potentials for BRM process. The quantum yield is significantly enhanced with BRM in the monolithic honeycomb photoreactor loaded with Ag-La modified pCNNTs due to greater photon energy utilization, larger illuminated surface area, improved sorption process and surface reactions with efficient charge carrier utilization for CO2 reduction and CH4/H2O oxidation. Reaction mechanism is proposed to commensurate with the performance of Ag-La/pCNNT for BRM process based on characterization analysis and experimental results. The experimental results could provide guidance for further development of advanced and highly efficient hetero-structures for photocatalytic BRM applications.

Tunable Type I and II heterojunction of CoOx nanoparticles confined in g-C3N4 nanotubes for photocatalytic hydrogen production

This work reports tunable heterojunction architectures of cobalt oxides (CoOx) nanoparticles confined on well-arrayed graphitic carbon nitride nanotubes (C3N4 NTs) by using a facile one-pot method but under different annealing atmospheres. A Type II heterojunction of cobalt monoxide nanoparticles (CoO NPs)/C3N4 NTs was obtained after annealing under vacuum, and fine CoO NPs less than 8 nm in size were homogeneously anchored on the surface of C3N4 NTs. A Type I heterojunction of tricobalt tetraoxide (Co3O4)/C3N4 NTs were formed under air condition, and Co3O4 NPs in the size range of 20 to 80 nm were aggregated on the surface. The photocatalytic activities of these two heterojunctions were evaluated with hydrogen production from water splitting. The strategically developed CoO/C3N4 NTs with a 7 wt. % CoO shows the highest H2 yield under visible light irradiation and the best stability among the photocatalysts studied in this work. Comprehensive characterization results reveal that the superior performance of CoO/C3N4 NTs may be attributed to the uniformly distributed smaller nanoparticles on the well-arrayed nanotubes, the longer lifetime of excited electrons, the faster charge transfer and the stronger electronic interaction between the heterojunctions. Our Kelvin probe force microscopy results firmly verify that the CoO/C3N4 NT and Co3O4/C3N4 NT nanocomposites form a Type II and Type I heterojunction, respectively, and charge transfer pathways and reaction mechanisms are therefore established.

Bimetallic PtNi/g-C3N4 nanotubes with enhanced photocatalytic activity for H2 evolution under visible light irradiation

Bimetallic PtNi-decorated graphitic carbon nitride (g-C3N4) nanotubes were prepared through calcining the mixture of urea and thiourea in the presence of Pluronic F127, followed by deposition of bimetallic PtNi nanoparticles (NPs) via chemical reduction. It is found that the photocatalytic activity of PtNi/g-C3N4 nanotubes is strongly dependent on the molar ratio of Pt/Ni and the highest activity is observed for Pt1Ni1/g-C3N4. Under visible light (λ > 420 nm) irradiation, the H2 generation rate over Pt1Ni1/g-C3N4 nanotubes is 104.7 μmol h−1 from a triethanolamine (10 vol%) aqueous solution, which is higher than that of Pt/g-C3N4 nanotubes (98.6 μmol h−1) and is about 47.6 times higher than that of pure g-C3N4 nanotubes. The cyclic photocatalytic reaction indicates that our Pt1Ni1/g-C3N4 nanotubes function as a stable photocatalyst for visible light-driven H2 production. The effect of bimetallic PtNi NPs in the transfer and separation of photogenerated charge carriers occurring in the excited g-C3N4 nanotubes was investigated by performing photo-electrochemical and photoluminescence measurements. Our results reveal that bimetallic PtNi could replace Pt as a promising cocatalyst for photocatalytic H2 evolution with better performance and lower cost.

Wall-Mesoporous Graphitic Carbon Nitride Nanotubes for Efficient Photocatalytic Hydrogen Evolution.

Graphitic carbon nitride (g-CN) has attracted tremendous attention as visible-light photocatalyst. However, for further improving the catalytic activity, multilevel and hierarchical nanostructuring of g-CN is highly desirable to effectively expose active sites and facilitate separation and migration of photoexciteded charge carriers for largely enhanced photocatalytic behavior. Here, we prepare wall-mesoporous graphitic carbon nitride nanotubes (g-CNNTs) by in situ annealing of urea microrod arrays preformed in virtue of a vertical gradient freeze growth (VGFG) method. Benefiting from the distinctive structural features, the hierarchical g-CNNTs exhibit a high photocatalytic H2 production rate of 8789 μmol h-1 g-1 with an excellent apparent quantum yield of 6.3 % under visible-light irradiation and long-term cycling stability. This work provides a facile and eco-friendly strategy to prepare a new type of carbon nitride-based nanostructural material for photocatalysis and environmental remediation.

Photocatalytic self-cleaning carbon nitride nanotube intercalated reduced graphene oxide membranes for enhanced water purification

Crumpled laminar nanostructures with nanoscale water transport channels constructed by two-dimensional (2D) reduced graphene oxide nanosheets (rGO NS) have been considered as a promising membrane separation layer for water purification. However, efficient tuning of rGO laminar structures with enhanced membrane performance remains challenging. In this work, we report a novel 1D graphitic carbon nitride nanotube (g-C3N4 NT) intercalated rGO nanofiltration (NF) membrane with enhanced photo-induced self-cleaning performance. The g-C3N4 NT photocatalyst could not only enlarge the rGO interlayer spacing for improved water permeability, but also endow the composite membrane with visible-light photocatalytic activity for efficient removal of organic dyes from polluted water. Our g-C3N4 NT/rGO membrane exhibits superior water permeability (4.87 L·m−2·h−1·bar−1) and synergetic Rhodamine B (RhB) removal rate (>98%) for long-term operation, compared with pristine rGO membrane and 2D g-C3N4 NS intercalated rGO membrane prepared by the same method. The RhB removal mechanism on the as-prepared composite membranes under integrated photocatalytic filtration process is presented. Our findings offer new insights into designing and tuning laminar structures of photocatalytic graphene-based NF membranes for enhanced water purification.