Characterization of well-crystallized graphitic carbon nitride nanocrystallites via a benzene-thermal route at low temperatures

Reexamination of Solvothermal Synthesis of Layered Carbon Nitride

“…FT-IR spectrum of the g-C 3 N 4 powder also indicates the presence of hydrogen probably in the form of NH, as clearly mentioned in the original paper by Guo et al [18] (and also pointed out in our earlier paper [7]), although they did not discuss the origin of hydrogen. It is, therefore, highly questionable whether the product obtained by Guo et al 's recipe [18] is certainly hydrogen-free graphitic C 3 N 4 composed of the stacked layers of s-triazine building blocks. Meanwhile, Guo et al 's solvothermal recipe and characterization of the product by X-ray and electron diffraction and spectroscopic analyses have been cited by recent studies [30][31][32], where the authors assumed that their carbon nitride products have the ideal graphitic framework composed of striazine and heptazine units through the comparison with Guo et al 's result.…”

“…The HPHT experiments using the solvothermally prepared g-C 3 N 4 failed to synthesize any dense carbon nitride phases but instead resulted in the formation of a hydrogen-bearing, carbon nitride imide (C 2 N 2 (NH))-related phase [7]. FT-IR spectrum of the g-C 3 N 4 powder also indicates the presence of hydrogen probably in the form of NH, as clearly mentioned in the original paper by Guo et al [18] (and also pointed out in our earlier paper [7]), although they did not discuss the origin of hydrogen. It is, therefore, highly questionable whether the product obtained by Guo et al 's recipe [18] is certainly hydrogen-free graphitic C 3 N 4 composed of the stacked layers of s-triazine building blocks.…”

“…Nanocrystalline "graphitic" carbon nitride was prepared through the solvothermal reaction (1) between cyanuric chloride (C 3 N 3 Cl 3 ) and sodium amide (NaNH 2 ) by following the procedure reported by Guo et al [18]. Cyanuric chloride (99 %) and sodium amide (98 %) reagents purchased from Sigma-Aldrich Co. LLC were used.…”

“…Among these, one of the easiest and simplest ways to obtain a nanocrystalline powder of g-C 3 N 4 is the solvothermal method, in which the synthesis is achieved through the reaction of chemical sources in a solvent such as benzene and acetonitrile at high temperatures. In particular, a pioneer recipe reported by Guo et al [18] was commonly used in many previous studies (e.g., [7,[27][28][29]) to obtain nanocrystalline g-C 3 N 4 powders of various purposes. Their g-C 3 N 4 -forming reaction is expressed by the following formula:…”

“…In the past few decades, g-C 3 N 4 attracted considerable attention in industrial applications such as photocatalyst (e.g., [4]), hydrogen storage (e.g., [5]), semiconductor (e.g., [6]), and a starting material for synthesizing potential superhard carbon nitride phases (e.g., [7]). A number of reports have been published for the synthesis of g-C 3 N 4 and even other graphitic forms with nonstoichiometric compositions on the basis of various techniques such as CVD [8][9][10], solid reaction [11][12][13][14][15][16][17], solvothermal method [18][19][20][21][22], and thermal decomposition of compounds [23][24][25][26]. Among these, one of the easiest and simplest ways to obtain a nanocrystalline powder of g-C 3 N 4 is the solvothermal method, in which the synthesis is achieved through the reaction of chemical sources in a solvent such as benzene and acetonitrile at high temperatures.…”