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Importance of 2D Nanomaterials for Energy
Published in Ram K. Gupta, Energy Applications of 2D Nanomaterials, 2022
Sami Ullah, Faheem K. Butt, Junaid Ahmad
g-C3N4 is a well-structured polymer, which comprises nitrogen and carbon elements. It can be synthesized by using the various nitrogen-containing precursors, which are easily available and economically suitable such as melamine, cyanamide, urea, thiourea, and dicyandiamide. Various approaches have been employed for the production of g-C3N4 including solvothermal, plasma sputtering deposition, chemical vapor deposition, and thermal polycondensation. Among all these methods, thermal polycondensation has gained much attention owing to its economic and facile approach. The nitrogen containing little molecules can polymerize into g-C3N4 while in the process of simple calcination method at 450°C–650°C. Electronic band framework and structural properties of developed g-C3N4 mainly depend upon the type of precursor. For example, g-C3N4 developed from thiourea shows shorter bandgap as compared to developed from urea. Similarly, g-C3N4 obtained from urea exhibits larger specific surface area as compared to that developed from melamine [31].
Carbon-Based Materials
Published in Ghenadii Korotcenkov, Handbook of Humidity Measurement, 2020
Graphitic carbon nitride can be made by polymerization of cyanamide, dicyandiamide, or melamine (Thomas et al. 2008). Graphitic carbon nitride can also be prepared by electrodeposition on the Si(100) substrate from a saturated acetone solution of cyanuric trichloride and melamine (ratio = 1:1.5) at room temperature (Li et al. 2003b). Well-crystallized graphitic carbon nitride nanocrystallites can be also prepared via benzene-thermal reaction between C3N3Cl3 and NaNH2 at 180–220°C for 8–12 h (Guo et al. 2003). Recently, a new method of synthesis of graphitic carbon nitrides by heating at 400°C–600°C of a mixture of melamine and uric acid in the presence of alumina has been reported. Alumina favored the deposition of the graphitic carbon nitrides layers on the exposed surface. This method can be assimilated to an in-situ CVD (Dante et al. 2011).
Carbon Nanomaterials in Electrolysis and Hydrogen
Published in Shuhui Sun, Xueliang Sun, Zhongwei Chen, Yuyu Liu, David P. Wilkinson, Jiujun Zhang, Carbon Nanomaterials for Electrochemical Energy Technologies, 2017
Yuyu Liu, Hongbing Zhao, Rongzhi Chen, Jinli Qiao, David P. Wilkinson, Jiujun Zhang
g-C3N4 is a polymeric semiconductor material with tri-s-triazine (melem) as the basic building unit connected by planar amino groups. It has a graphite-like sp2-bonded C-N structure and behaves like a p-conjugated semiconductor (Figure 12.22). This polymer can be easily prepared by the thermal condensation of a few commonly available, low-cost, nitrogen-rich precursors, such as melamine, cyanamide, dicyandiamide, urea, or mixtures thereof. However, such a simple method typically results in irregular and dense g-C3N4 aggregates with low surface areas. Though it is one of the well-studied synthetic polymers, the widespread investigation of this material as a catalyst for the water-splitting reaction has started only recently after the work by Wang and co-workers [168]. The bandgap of the bright yellow powder was measured to be 2.7 eV, with the conduction band (CB) and valence band (VB) positions located so as to be energetically possible for water splitting.
Application of a calcined animal bone to synthesis of graphitic carbon nitride composite
Published in Environmental Technology, 2022
Graphitic carbon nitride (g-C3N4), a polymeric organic semiconductor with a graphite-like layered structure, has been extensively studied due to its unique features such as facile synthesis, low cost, biocompatibility, nontoxicity, metal-free component, tailorable physicochemical properties, medium band gap for visible-light absorption, and electric band structures favourable for a variety of chemical reactions [1–9]. Owing to these features, g-C3N4 can be applied to a wide range of applications including solar cells [1,4], sensors [1,4,7,10], air purification [1,3,5,7,10], water purification [1–3,5,7,9,10–12], electronic devices [1,3,5,10], battery devices [1,3,10], bacterial inactivation [1,3–5,7], nitrogen fixation [13,14], CO2 reduction [1–7], and hydrogen generation [1–8,10]. Although g-C3N4 can be easily synthesized via the thermal condensation of N-rich precursors such as cyanamide, dicyandiamide, melamine, thiourea, urea, or mixtures of these materials [1–10,15], the g-C3N4 generated via this method is usually bulky, and has a low specific surface area, a fast recombination of photogenerated electron-lone pairs, and a poor photocatalytic activity [1–10].
Mesoporous graphitic carbon nitride for adsorptive desulfurization in an isooctane solution
Published in Journal of Sulfur Chemistry, 2022
Xianli Huang, Yueyue Zhang, Yue Lai, Yang Li
With continuing advances in materials science, an increasing number of new functional materials have been applied for the adsorption process, e.g. graphitic carbon nitride (g-C3N4) [18,19]. To date, g-C3N4 has drawn much scientific attention due to its environment-friendly superiority. Usually, g-C3N4 is widely used as a metal-free photocatalyst in the field of hydrogen evolution, water splitting or pollutant destruction and so on [20,21]. The pyrolysis of precursors rich in carbon and nitrogen, such as dicyandiamide [22,23], cyanamide [24–26], thiourea [27,28], urea [29,30] and melamine [31] is utilized extensively. However, the low specific surface area is a big hurdle. Due to the graphitic layered structure, the surface area of g-C3N4 prepared by direct polycondensation of C-, N- and H-containing precursors is normally low (ca. 10m2/g) [32]. Different methods have been applied to overcome this disadvantage, like the formation of nano-architectures [33]. We have attempted to synthesize mesoporous g-C3N4 with large surface areas and accidentally found its outstanding porous structures have good adsorption ability towards sulfur compounds during an adsorptive desulfurization process [34].
Organocatalysis with carbon nitrides
Published in Science and Technology of Advanced Materials, 2023
Sujanya Maria Ruban, Kavitha Ramadass, Gurwinder Singh, Siddulu Naidu Talapaneni, Gunda Kamalakar, Chandrakanth Rajanna Gadipelly, Lakshmi Kantham Mannepalli, Yoshihiro Sugi, Ajayan Vinu
Various methods including physical vapor deposition, chemical vapor deposition, thermal polymerization-condensation, and hydrothermal or solvothermal methods are available for the synthesis of g-C3N4 [44]. Among these methods, thermal polymerization-condensation is the most used synthesis technique for preparing carbon nitrides and the widely used precursors are urea, melamine, dicyandiamide, cyanamide thiourea, and cyanuric acid [45,46]. Polyaddition and polycondensation are the processes involved in carbon nitride synthesis, which are temperature dependent. Polyaddition is the polymerization process to convert precursors into melamine whereas polycondensation is the condensation of the melamine by the loss of ammonia to form a g-C3N4 polymer [42,44]. The carbon nitrides derived from the traditional thermal condensation method have a low surface area (>20 m2/g), highly conjugated stacking of nitrogen atoms in the heptazine structure, and nitrogen atoms with less basicity, less bridging nitrogen atoms and less defective sites at the edges for the graphitic structure. The structure of the g-C3N4 may contain the molecular units of s-heptazine (tri-s-triazine) and triazine [47]. Triazine is not as stable as the tri-s-triazine (s-heptazine) structure. For catalytic applications, g-C3N4 with tri-s-triazine units may be more beneficial as it has more nitrogen atoms, providing more anchoring and active sites for catalytic reactions. Owing to the stability and other benefits of the tri-s-triazine structure, synthesizing carbon nitrides with tri-s-triazine molecular units is given more attention [48,49].