Papers by Keyword: Carbon Nitride

Abstract: The incorporation of quasi-atomic Ni (OH)₂ clusters onto graphitic C₃N₄ (gCN) remarkably enhances the photocatalytic production of hydrogen peroxide (H₂O₂) and benzaldehyde (BAL) from benzyl alcohol (BA) in water under visible light at 440 nm. Upon loading Ni (OH)₂, H₂O₂ production reaches 306 µmol g⁻¹ h⁻¹ and BAL production reaches 270 µmol L⁻¹ h⁻¹. The high photocatalytic performance is attributed to the formation of ultrasmall clusters of Ni (OH)₂, which reduce recombination by trapping holes, thereby increasing the activity (BA conversion). Efficient hole transfer to BA is also facilitated, enhancing selectivity (BAL selectivity). Upon the addition of Ni (OH)₂, the steady-state electron population photoexcited by visible light increases 5.5-fold. The proposed modification of gCN with Ni achieves nearly 100% efficiency in both activity and selectivity to produce H₂O₂, while also generating BAL, a value-added product. This demonstrates its potential for sustainable chemical transformations using visible light and water as a green solvent.

Abstract: Carbon nitride (C₃N₄) has gained attention from scientists due to its potential applications as a catalyst for organic synthesis, electrodes, photocatalysts, and hydrogen storage materials. Using C₃N₄ as a photocatalyst for the glycerol-to-hydrogen reaction could offer many development advantages. Pure C₃N₄ has several shortcomings as a photocatalyst, so modifications are needed to enhance its properties and characteristics. Converting C₃N₄ into nanosheet form and adding Zirconium doping are solutions to improve its performance. The nanosheet form increases the surface area by creating thin sheet structures, while Zirconium doping is chosen because it can improve the conductivity and mechanical properties of the catalyst. This research focuses on characterizing catalysts with varying doping levels (5%, 10%, 15%, 20%, and 27%). Tests conducted include BET analysis, XRD, and UV-Vis DRS. Results show that the sample with 20% doping performs the best, with a specific surface area of 46.087 m²/g. Crystallinity was assessed with values of 2Ө = 27.8426°, 31.6712°, 45.4188°, and 56.4368°. The band gap energy was determined to be 3.067 eV. These findings are then compared with previous research.

Abstract: Silver nanoparticles (Ag NPs) may increase photocatalytic activity of widely used photocatalysts under visible light irradiation and decrease recombination probability of photogenerated electrons and holes. In this paper, we report three different preparation methods to obtain Ag/C₃N₄ nanocomposites. We used Ag nanoparticles a) synthesized by using sodium borohydride, b) synthesized by using UV 365 nm LED and c) already prepared and purchased from company nanoIron. The Ag NPs have been loaded on thermally exfoliated carbon nitride with the aim to form 5 wt.% Ag/C₃N₄ nanocomposites. Further their photocatalytic activity was tested towards Indigo carmine dye (IC) under 416 nm LED. The results show that method a) loaded different amount and size of Ag NPs on the surface of C₃N₄, b) changed optoelectronic behaviors of nanocomposites and c) significantly influenced their photocatalytic activity.

Abstract: Amorphous carbonitride coatings (a-C:N and a-C:N:H) with dopant of niobium (Nb) were deposited on substrates of JIS SKH51 high speed steel (HSS) by a four-target close-field unbalance magnetron sputtering system. Subsequently, they were characterized by GDOS, XRD and XPS, and their corrosion resistance was comparatively evaluated. An electro-chemical tester was used to evaluate the corrosive behavior. An SEM was used to examine the test surface. The results revealed that the Nb dopant provided improvements in the corrosive performance to both the a-C:N and a-C:N:H coatings.

Abstract: This study discusses the mechanical and tribological properties of a series of carbon nitride coatings deposited by unbalanced DC magnetron sputtering using nitrogen-argon mixture gas and graphite targets. The carbon nitride coatings were with varying carbon/nitrogen ratio by varying the gas flow rate ratio of nitrogen gas/argon while kept the overall gas flow rate at constant. The carbon nitride coatings with C/N ratios from 2.01 to 3.27 were obtained. The coatings were characterized and studied by nanohardness, scratching, and wear testers. It was found that the carbon nitride coatings with C/N ratio=2.36 showed the best performance of all the evaluated properties.

Abstract: In this work, a novel and facile sequential cation-exchanging strategy was developed to synthesize phosphorus doped g-C₃N₄ nanotubes, and resulted nanotubes were composed of small nanorods with length of several hundred nanometers by oriented aggregation. As obtained products exhibit greatly enhanced photocatalytic hydrogen evolution with rate of 4.59 mmol h^-1 g^-1, which is 16 times higher than that of the bulk g-C₃N₄ under visible light irradiation. Mechanism investigation reveals that the superior photocatalytic property could be attributed to its improved visible light absorbance, well suppressed charges recombination and nanostructural construction.

Abstract: 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.

Abstract: Carbon nitride coatings doped with tungsten were deposited on high speed steel disks by unbalanced DC magnetron sputtering using nitrogen-argon mixture gas. The coatings were deposited on three different types of interlayer (Ti, Ti/TiN and Ti/TiC), and the tungsten target current was varied from 0 to 0.9 A. Surface morphology of the coatings were measured by roughness testing and scanning electron microscopy (SEM). In addition, the chemical composition and depth profile were analyzed by X-ray Diffraction (XRD) analysis, Raman spectroscopy, and glow discharge spectroscopy (GDS). Finally, the hardness (H) and elasticity (E) were measured by nanoindentation and a Rockwell indentation test, while the tribological properties were tested using a pin-on-disk tribometer. After all, the coatings were measured by cutting testing of tuning inserts and micro-drillers. It is found that all of the coatings are amorphous and have a thickness of approximately 1.5 μm. Moreover, the nitrogen content is around 30 at%, while the tungsten content varies in the range of 0-9 at%. In addition, the hardness values are in the range of 15-20 GPa and the elasticity varies from 236 to 274 GPa. A good correlation is observed between the wear resistance and the indentation adhesion level. Furthermore, it is found that the hardness is not significantly correlated to the tungsten content and the coatings deposited on the Ti/TiC interlayer have greater adhesion. Finally, the coatings generally have a very low coefficient of friction (0.01-0.3) and a wear coefficient as low as 10^-6 mm³/Nm, and the CN/TiC coating reduced 41% and 43% of flank wear in the cutting testing of turning inserts and micro-drillers respectively.

Abstract: The graphitic carbon nitride (g-C₃N₄) materials have been synthesized from nitrogen rich precursors such as urea and thiourea by directly heating at 520 °C for 2 h. The as-synthesized carbon nitride samples were characterized by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible (UV-vis) absorption spectroscopy, photoluminescence (PL) and particle size analysis. The photoelectrochemical measurements were performed using several on-off cycles under visible-light irradiation. The x-ray diffraction peak is broader which indicates the fine powder nature of the synthesized materials. The estimated crystallite size of carbon nitrides synthesized from urea (U-CN) and thiourea (T-CN) are 4.0 and 4.4 nm respectively. The particle size of U-CN and T-CN were analysed by particle size analyser and were found to be 57.3 and 273.3 nm respectively. The photocatalytic activity for the degradation of the textile dye namely, direct red-81 (DR81) using these carbon nitrides were carried out under visible light irradiation. In the present investigation, a comparison study on the carbon nitrides synthesized from cheap precursors such as urea and thiourea for the degradation of DR81 has been carried out. The results inferred that U-CN exhibited higher photocatalytic activity than T-CN. The photoelectrochemical studies confirmed that the (e^--h⁺) charge carrier separation is more efficient in U-CN than that of T-CN and therefore showed high photocatalytic degradation. Further, the smaller particle size of U-CN is also responsible for the observed degradation trend.

Abstract: Carbon based materials have attracted much for its unique surface microstructure and nanomechanical properties among researchers. In this study, the influence of microstructure on the nanomechanical properties of thin carbon based films was studied in detail. For which amorphous Carbon nitride (a-CN) and Titanium incorporated amorphous Carbon nitride (Ti/a-CN) thin films were prepared with a thickness of less than 100 nm using hybrid ion beam deposition technique. The incorporation of Ti into the a-CN matrix greatly modified the sp³/sp² hybridized bonding ratio and it is reflected in the mechanical hardness of Ti/a-CN thin film. Most of the incorporated Ti reacts with carbon and nitrogen to form TiN and TiCN phases respectively. On the other hand, owing to the usage of energetic ion bombardment and the presence of TiN/TiCN phases in the carbon nitride matrix, the Ti/a-CN nanocomposite film shows improved adhesion strength compared to that of pure a-CN film. Overall the presence of hard metallic phase in the amorphous carbon network alters the microstructure and improves the adhesion strength of a-CN films suitable for protective coating applications.