Graphitic Carbon Nitride Nanotubes Research Articles

Scalable fabrication of high surface area g-C3N4 nanotubes for efficient photocatalytic hydrogen production

In this research, we present a novel facile, scalable, and template-free technique of synthesizing graphitic carbon nitride (g-C3N4) nanotubes for generating hydrogen through photocatalysis. The hybrid technique involves a two-fold mixing of the precursor materials melamine (M) and cyanuric acid (CA), involving ball milling followed by solution mixing. By varying the M:CA molar ratios, different compositions of g-C3N4 nanotubes were fabricated. The study focused on examining the surface characteristics and the photocatalytic hydrogen evolution performance of these nanotubes. Nanotubes with high specific surface area of 206 m2 g−1 for M:CA molar ratio of 1:3 and 178 m2 g−1 for M:CA molar ratio of 1:5 were produced, with H2 evolution rates of 543 μmol h−1 g−1 and 740 μmol h−1 g−1 respectively, which were an increase of 4 and 5-fold, respectively, in comparison to the pristine sample. The enhanced efficiency of hydrogen production through photocatalysis by nanotubes, when contrasted with pristine material, can be ascribed to their high crystallinity, superior specific surface areas, decreased recombination rates of electron-hole pairs generated during light exposure, and improved dynamics of charge carriers. This hybrid technique provides a new pathway for cost-effective fabrication of g-C3N4 nanotubes with substantial surface areas and high yield photocatalysts on an industrial scale, without the use of templates and hydrothermal processes for efficient hydrogen generation.

Fabrication of CdS NRs /MoS2@g-C3N4 nanotubes for efficient photoelectrochemical hydrogen production

Exploration of noble metal-free and highly efficient photoelectrocatalyst for hydrogen production attracts the attention of researchers. The graphitic carbon nitride nanotubes, cadmium sulfide nanorods (NRs) and molybedun disulfide, CdS NRs/MoS2@g-C3N4 nanotubes were synthesized via facile hydrothermal method for hydrogen production studies. The synthesized CdS NRs/MoS2@g-C3N4 nanotubes were studied for electrochemical hydrogen production applications. Structural data revealed that the synthesized composite materials attained crystallinity. Electrochemical investigations demonstrated the highest hydrogen production efficiency of CdS NRs/MoS2@g-C3N4 nanotubes as compared to the bare graphitic carbon nitride nanotubes. This seems that the modification of g-C3N4 NTs with MoS2 increased the photocatalytic efficiency of g-C3N4 NTs. The good efficiency of the CdS NRs/MoS2@g-C3N4 NTs is owing to a unique tubular structure, the presence of active sites, light reflection channel, nanotube composite heterostructure, electron-hole separation, better charge transfer and the synergistic effect. Moreover, it was observed that the tubular structure would be the best photoelectrocatalyst for hydrogen production achieving a geometric current density of 10 mAcm−2 at an overpotential of 0.81 V gives 144 mVdec−1 in 1 M KOH versus the RHE. These results may provide insights into constructing highly efficient photoelectrocatalysts by varying the structural morphology and heterojunction for hydrogen production.

Sensitive and fast electrochemical recognition of nitroaromatic explosives in liquid phase using ultrathin graphitic carbon nitride nanotubes

In the present work, a simple, effective method to synthesis high-quality carbon nitride nanotubes with ∼90 nm diameter and 5–9 nm in thickness along with a high-yield (63 %) via template-free hydrothermal synthesis is reported. By using these graphitic carbon nitride nanotubes an advanced electrochemical sensor was demonstrated to selectively sense explosive 2,4-dinitrotoluene. It is demonstrated that bigger linear range towards 2,4-dinitrotoluene, sensing up to 425 μM is reported. Furthermore, the experiments demonstrated that this sensor possesses a high sensitivity not only for 2,4-dinitrotoluene but also for other nitroaromatic explosives.

G-C3N4/TiO2 nanotube array for enhanced photoelectrochemical water splitting

Graphitic carbon nitride (g-C3N4) and TiO2 nanotubes (TNT) have made significant breakthroughs in the field of photocatalysis because of their unique features, such as environmental friendliness, low cost and good stability. Herein, we present the improved photo-electrochemical performance under AM 1.5G irradiation of three different photoanodes based on TNT coated with g-C3N4 via the effortless thermal treatment of anodized TNT sheets over melamine (TNT-M), urea (TNT-U) and dicyanamide (TNT -D). A maximum photocurrent of up to 0.14 mA cm−2 at 1.23 V (vs. RHE) is obtained under illumination using AM 1.5 G light source for TNT-D, which is ten times greater than pristine TNT (0.014 mA cm−2). A good photoelectrochemical stability with efficient charge transfer is observed, and electrochemical impedance spectra reveal that better photoelectrochemical performance is due to the reduced electron-hole pair recombination via the development of heterojunction between TNT and g-C3N4 compared to the bare-TNT electrode.

Lignin-modified graphitic carbon nitride nanotubes for photocatalytic H2O2 production and degradation of brilliant black BN

As a renewable aromatic compound with enormous production potential, lignin has various potential high-value utilization pathways, but the success achieved in the field of photocatalysis is limited. Herein, this work prepares a new type of photocatalyst by modifying Graphitic Carbon Nitride Nanotubes (CNT) with self-assembled lignin nanospheres for the photocatalytic production of H2O2 and the degradation of azo dyes. Under light conditions, lignin enhances the production of H2O2 through oxygen reduction and collaborates with carbon nitride tubes to generate O2− and 1O2. Furthermore, carbon nitride tubes form electron-rich regions with lignin, promoting the transfer of electrons from adsorbed aromatic pollutants to this region, thereby facilitating their degradation. The experimental results indicate that the addition of 5 % lignin significantly enhances the photocatalytic degradation efficiency of azo dyes, with a degradation rate 1.87 times higher than that of the original carbon nitride tubes. Furthermore, CNL also have excellent degradation ability to pollutants in actual wastewater. This study provides new insights and prospects for the high-value utilization of lignin, enabling it to be used as a photocatalytic co-catalyst to participate in the photocatalytic degradation of environmental pollutants.

Recyclable bactericidal packaging films for emperor banana preservation

Food safety issues and food waste have always been hot topics of concern. This study aimed to develop a recyclable bactericidal packaging film that combines polylactic acid (PLA), graphitic carbon nitride (CN) and carbon nanotubes (CNT) to extend food shelf life. This film exhibited compactness and thermostability, as observed by scanning electron microscope and differential scanning calorimeter. The temperature of P/CN/CNT film could still reach 54 ± 4 °C after being used for 3 times. The film still has bactericidal activity on the 5th cycle use except for L. monocytogenes revealed by morphological characterization on bacteria. This film effectively extended the shelf life of banana to 7 days, as confirmed by measurements of hardness, pH value and total bacterial count of banana. This study provides a packaging film with recyclable bactericidal ability.

Three-dimensional rGO/CNT/g-C3N4 macro discs as an efficient peroxymonosulfate activator for catalytic degradation of sulfamethoxazole

Over the past few years, advanced oxidation processes (AOPs) have shown promising efficiencies for wastewater remediation. Carbocatalysis, in particular, has been exploited widely thanks to its sustainable and economical properties but has an issue of recovery and reusability of the catalysts. To address this, three-dimensional (3D) binary and ternary graphene-based composites in the form of macro discs were created to activate peroxymonosulfate (PMS) for catalytic oxidation of sulfamethoxazole (SMX). Graphene oxide served as the base, while graphitic carbon nitride (g-C3N4) and/or single-walled carbon nanotubes (SWCNTs) were added. Among the various discs synthesized, rGNTCN discs (ternary composite) were proven to be the most efficient by completely degrading SMX in 60 min owing to their large surface area and nitrogen loading. The catalytic system was further optimized by varying the reaction parameters, and selective radical quenching and electron paramagnetic resonance tests were performed to identify the active radical, revealing the synergistic role of both radical and non-radical pathways. This led to the development of possible SMX degradation pathways. This research not only provides insights into ternary carbocatalysis but also gives a novel breakthrough in catalyst recovery and reusability by transforming nanocatalysts into macro catalysts.

Electronic and energy level structural engineering of graphitic carbon nitride nanotubes with B and S co-doping for photocatalytic hydrogen evolution

The ideal photocatalyst used for photocatalytic water splitting requires strong light absorption, fast charge separation/transfer ability and abundant active sites. Heteroatom doping offers a promising and rational approach to optimize the photocatalytic activity. However, achieving high photocatalytic performance remains challenging if just relying on single-element doping. Herein, Boron (B) and sulfur (S) dopants are simultaneously introduced into graphitic carbon nitride (g-C3N4) nanotubes by supramolecular self­assembly strategy. The developed B and S co-doped g-C3N4 nanotubes (B,S-TCN) exhibited an outstanding photocatalytic performance in the conversion of H2O into H2 (9.321 mmol g−1h−1), and the corresponding external quantum efficiency (EQE) reached 5.3% under the irradiation of λ = 420 nm. It is well evidenced by the closely combined experimental and (density functional theory) DFT calculations: (1) the introduction of B dopants can facilitate H2O adsorption and drive interatomic electron transfer, leading to efficient water splitting reaction. (2) S dopants can stretch the VB position to promote the oxidation ability of g-C3N4, which can accelerate the consumption of holes and thus inhibit the recombination with electrons. (3) the simultaneous introduction of B and S can engineer the electronic and energy level structural of g-C3N4 for optimizing interior charge transfer. Finally, the purpose of maximizing photocatalytic performance is achieved.

A detailed experimental comparison on the hydrogen storage ability of different forms of graphitic carbon nitride (bulk, nanotubes and sheets) with multiwalled carbon nanotubes

The reversible hydrogen storage of graphitic carbon nitride (g-C3N4) nanotubes at room temperature was first studied through experimental methods in this work and was compared to multiwalled carbon nanotubes (MWCNT), bulk g-C3N4, and g-C3N4 nanosheets. Compared with MWCNT which had a similar specific surface area around 60 m2/g, g-C3N4 nanotubes had a higher room temperature hydrogen storage capacity up from 0.46 wt% for MWCNT to 0.78 wt%. This value for the g-C3N4 nanotubes was also higher than the hydrogen storage capacity of bulk g-C3N4 (0.51 wt%) and g-C3N4 nanosheets (0.73 wt%), even though g-C3N4 nanosheets had the highest specific surface area of 161 m2/g. Temperature programming desorption (TPD) was applied to study the desorption behaviours and it was found that chemisorption contributed to the relative high storage capacity of g-C3N4 nanotubes.

In-situ growth of MoS2 nanosheets on g-C3N4 nanotube: A novel electrochemical sensing platform for vanillin determination in food samples

The molybdenum disulfide (MoS2) based nanomaterials show outstanding catalytic performance in many electrochemical sensing applications with improved catalytic and electrochemical properties. Novel electrocatalyst developments and their application for food additives monitoring are of significant interest. In this work, we have developed a novel synthesis protocol for graphitic carbon nitride nanotubes decorated MoS2 composite (g-C3N4 NTs@MoS2) using the hydrothermal method and evaluated its electrochemical sensing performance towards vanillin (VN) determination. The electrochemical sensor was accomplished at various electrolytes and optimized parameters to get an enhanced current signal for VN detection. Under the optimized conditions, the sensor obtained wide linear ranges (0.005-458.9 µM), low limit of detection (LOD, 4 nM), and excellent sensitivity (3.48 μA μM−1 cm−2) using differential pulse voltammetry (DPV). Moreover, the practical applicability of the developed sensor was also successfully evaluated in food samples with an excellent recovery rate.

Microstructure regulation of graphitic carbon nitride nanotubes via quick thermal polymerization process for photocatalytic hydrogen evolution

Among multitudinous photocatalytic materials, graphite carbonitride (g-C3N4) has been widely explored as a new photocatalyst. The g-C3N4 nanotubes with hollow one-dimensional structure can promote carrier migration along the one-dimensional direction, thereby improving the electron-hole separation efficiency, which has always been a hot spot. However, the collapse of nanotubes in long-term thermal polymerization process leads to the decline of photocatalytic performance, which is expected to be further optimized. Herein, we report g-C3N4 nanotubes (TCN) through short time thermal polymerization to ensure the integrity of g-C3N4 skeleton. And the influence of thermal temperature on the internal formation mechanism of nanotube morphology is investigated. Combined with the unique hollow tube structure and complete framework, the migration of photogenerated carriers is significantly accelerated and the photocatalytic hydrogen evolution performance is improved more than 7 times compared with the original g-C3N4. This work provides novel insights into the preparation of g-C3N4 nanotubes for photocatalytic applications.

Synergistic effect of gold NPs modified graphitic carbon nitride nanotubes (g-CNT) with the role of hot electrons and hole scavengers for boosting solar hydrogen production

The efficient and selective photocatalysts for the evolution of hydrogen are highly demanding, however, many semiconductors are complex in nature and have lower photocatalytic efficiency. This is because of their small exposed surface area, poor light penetration, and unregulated charge recombination rate. Herein, well-designed graphitic carbon nitride with hierarchical nanotextures loaded with plasmonic gold (Au) nanoparticles has been investigated for stimulating photocatalytic H2 evolution. Hole scavengers, diffusion effects, duration, and mass transfer were used to evaluate the photoactivity activity in a slurry type continuous flow photoreactor system. Due to better charge carrier separation and enhanced light permeability, H2 evolution was boosted by two times when bulk g-C3N4 structure was alternated with graphitic carbon nitride nanotubes (g-CNT). The maximum H2 generation rate was 455 μmol g−1 h−1 with 0.3% Au/g-CNT nanotexture, which was 17.8 and 8.9 times greater than utilizing g-C3N4 and g-CNT samples, respectively. The key factors influencing this improvement in photoactivity were the unique interlayer opening, higher light penetration, more light utilization due to plasmonic effect, enhanced surface reactive active sites, and decreased charge carrier recombination. The hot electrons due to plasmonic gold was another important feature to promote H2 evolution rate under solar energy. It is possible to employ these freshly developed nanotextures, which have a gold plasmonic effect, for solar energy conversion and other energy-related applications.

Nanoarchitectonics of Ag-modified g-C3N4@halloysite nanotubes by a green method for enhanced photocatalytic efficiency

In this study, a facile and cost effective green synthesis has been utilized for the synthesis of silver nanoparticles (Ag-NPs)–modified graphitic carbon nitride (Ag-g-C3N4) and halloysite nanotubes (HNTs) using Centella Asiatica (L.) extract, urea and mineral source of natural halloysite (HNTs), respectively. Here, silver ions (Ag+) were reduced to Ag-NPs using an aqueous Centella Asiatica (L.) as reducing and capping agent. The synthesized Ag-g-C3N4@HNTs were characterized by various physiochemical methods such as XRD, FT-IR, BET, SEM, TEM, EDS–mapping, UV–vis-DRS, PL, XPS and EPR methods. In the photocatalytic experiment, Ag-g-C3N4@HNTs nanocomposite with silver surface plasmon resonance of Ag-NPs and multi-layer hollow nanotubes was outperformed by the individual components. With an in-depth study on the photocatalytic mechanisms, we can conclude that the enhanced performance of the nanocomposite is due to the effective separation of photogenerated electrons and superoxide radicals (•O2–) in water molecules. The photocatalyst preserved excellent photostability for up to four cycles (with a minor activity reduction from 95% to 91%). These results demonstrated the development of novel semiconductors from inexpensive resources with effective photoactivity to mitigate environmental problems.

O, S-g-C3N4 nanotubes as photovoltaic boosters in quantum dot-sensitized all-weather solar cells: a synergistic approach for enhanced power conversion efficiency in dark-light conditions

All up-to-the-minute solar cells generate highly efficient electricity under sunlight. However, the power outputs are ∼ zero under dark conditions due to the relatively low visible light intensity. We report high-performance quantum dots-sanitized all-weather solar cells (QDSSCs). The devices were based on rationally designed carbon quantum dots (CQDs) decorated oxygen and sulfur co-doped graphitic carbon nitride nanotubes (O, S-g-C3N4 NTs)-sensitized TiO2/long-persistence phosphor (LPP) photoanodes and Pt counter electrodes (CE). O, S-doped-g-C3N4 NTs can act as photo-boosters as well as the blocking layer to prevent the backflow of photoexcited electrons and prevent their recombination with the electrolyte. LPPs can store unabsorbed light ranging from visible to infrared light across the photoanode and convert it into green fluorescence, ultimately persistent CQDs/O, S-g-C3N4 NTs irradiation, and electricity generation under sunlight illumination in all light-dark environments. The maximum PCE was 18.5% for the device 7-CC/L prepared with a composite of CQDs and O, S-g-C3N4 NTs with an optimized weight of 7 mg and 0.2 g, respectively.

Insights into the function of semi-metallic 1T’ phase ReS2 as cocatalyst decorated g-C3N4 nanotubes for enhanced photocatalytic hydrogen production activity

In this paper, the semi-metallic 1T’ phase rhenium disulfide (ReS2) nanosheets (NSs) as cocatalysts are loading on the graphitic carbon nitride (g-C3N4) nanotubes (NTs) for photocatalytic hydrogen (H2) production. The as-prepared 1T′-ReS2/g-C3N4 composites present expressively enhanced photocatalytic activity. The 1T′-ReS2/g-C3N4 composite with 12 wt% 1T′-ReS2 exhibits the best photocatalytic H2 evolution performance (2275 μmol h−1 g−1), about 37 times of g-C3N4 NTs, 4 times of 2H-ReS2/g-C3N4 NTs, 6.7 times of 1T-ReS2/g-C3N4 NTs and 1.2 times of Pt/g-C3N4 NTs. Meanwhile, the apparent quantum yield (AQE) values of 1T′-ReS2/g-C3N4 (12 wt%) using 50 mg photocatalyst are 6.44% and 3.45% under light at λ = 370 nm and 456 nm, respectively. The activity tests and the DFT calculations prove that 1T′-ReS2/g-C3N4 composites have the following advantages: 1) The hollow porous g-C3N4 nanotubes are beneficial for improving the absorption and utilization of light, and the migration of photoexcited electrons; 2) After loading 1T′-ReS2 nanosheets on the g-C3N4 nanotubes, the 1T′-ReS2/g-C3N4 composites show the enhanced light absorption and fast carriers transfer, proving that the conductive 1T′-ReS2 nanosheets as cocatalysts could facilitate g-C3N4 nanotubes to generate more photoexcited charges, promote the carrier migration and separation, and supply abundant active sites for photocatalysis.

Activation of Fe species on graphitic carbon nitride nanotubes for efficient photocatalytic ammonia synthesis

Photocatalytic ammonia synthesis, as a suitable alternative to traditional Haber-Bosch artificial nitrogen reduction process, has aroused widespread interest. Graphitic carbon nitride (g-C3N4) has emerged as an attractive metal-free photocatalyst, but its development in photocatalytic ammonia synthesis field is greatly shackled to the low photocatalytic activity. In this work, a highly active Fe-doped tubular graphitic carbon nitride (Fe-TCN) is reported, which demonstrates transformative performance on photosynthesis of NH3 from N2. Such excellent photocatalytic activity is derived from the incorporation of Fe species as the active sites to efficiently adsorb and activate N2 molecules on the surface of TCN. Simultaneously, surface-active Fe species are also regarded as the trap sites of electrons, and the concentrated electrons at surface-active Fe species can significantly improve the NH3 conversion efficiency. Impressively, Fe-TCN realized a 9.5-fold enhancement of NH3 production rate with the yield of 647 μmol g−1 h−1 (λ ≥ 420 nm), and the corresponding reaction pathways are also established.

Carbon quantum dots-embedded graphitic carbon nitride nanotubes for enhancing the power conversion efficiency of sensitized solar cells

Graphitic carbon nitride (CN) has been widely used as a photocatalyst. Very few researchers have reported the use of CN in quantum dot-sensitized solar cells (QDSCs). In this study, we prepared nitrogen-rich carbon quantum dot (CQD)-embedded CN nanotubes (CCNTs) with freeze-dried urea and CQD precursors. The prepared CCNTs were used as efficient light harvesters in QDSCs for the first time; their use significantly improved the power conversion efficiency (PCE) of the solar cells compared to those of CQD, CN NT, and bulk CN-sensitized solar cells. The CCNT-sensitized solar cell exhibits 1.01% PCE, which is the highest value among carbon-based QDSCs. Moreover, the CCNTs-sensitized device showed superior photostability over those of CQDs-, CN NTs-, and bulk CN-sensitized devices. The improved performance of the CCNT-sensitized solar cell can be attributed to the facilitated photoelectron transport and suppressed charge recombination. The integration of nitrogen-rich CQDs in CCNTs adjusts the band alignment and maximizes the visible light harvest by reducing the energy barriers, which improves the charge collection efficiency of the device.

Graphitic carbon nitride and carbon nanotubes modified active carbon fiber cathode with enhanced H2O2 production and recycle of Fe3+/Fe2+ for electro-Fenton treatment of landfill leachate concentrate

g-C3N4/CNTs/ACF with improved H2O2 production and Fe2+ regeneration showed an excellent performance in the treatment of landfill leachate concentrate.

Bi-doped graphitic carbon nitride nanotubes boost the photocatalytic degradation of Rhodamine B

Polymeric carbon nitride (PCN) is an emerging metal-free photocatalyst with high stability but is plagued by low photocatalytic efficiency due to the rapid charge carrier recombination behavior.

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.