Influence of High Temperature Synthesis on the Structure of Graphitic Carbon Nitride and Its Hydrogen Generation Ability

Abstract

Graphitic carbon nitride (g-C3N4) was obtained by thermal polymerization of dicyandiamide, thiourea or melamine at high temperatures (550 and 600 °C), using different heating rates (2 or 10 °C min−1) and synthesis times (0 or 4 h). The effects of the synthesis conditions and type of the precursor on the efficiency of g-C3N4 were studied. The most efficient was the synthesis from dicyandiamide, 53%, while the efficiency in the process of synthesis from melamine and thiourea were much smaller, 26% and 11%, respectively. On the basis of the results provided by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), infrared spectroscopy (FTIR), ultraviolet–visible spectroscopy (UV–vis), thermogravimetric analysis (TGA), elemental analysis (EA), the best precursor and the optimum conditions of synthesis of g-C3N4 were identified to get the product of the most stable structure, the highest degree of ordering and condensation of structure and finally the highest photocatalytic activity. It was found that as the proton concentration decreased and the degree of condensation increased, the hydrogen yields during the photocatalytic decomposition of water–methanol solution were significantly enhanced. The generation of hydrogen was 1200 µmol g−1 and the selectivity towards hydrogen of more than 98%.

Reductive Modification of Carbon Nitride Structure by Metals—The Influence on Structure and Photocatalytic Hydrogen Evolution

“…Therefore, as a better option, it can be utilized as a sacrificial agent in the photocatalytic decomposition of water [25]. Our earlier results [19] suggested that g-C 3 N 4 can be an interesting alternative to the commonly used photocatalysts in water/methanol decomposition.…”

“…In addition, the production by condensation of simple nitrogen-rich compounds such as urea [13,14], thiourea [15], melamine [16,17], and dicyandiamide (DCDA) [18] is easy and cheap. Its additional advantage is that, depending on the type of precursor and condensation conditions, final carbon nitride can have different physicochemical properties [19]. Since the first reports on the photocatalytic properties of g-C 3 N 4 [20], attempts have been made to enhance its effectiveness, mainly by the addition of heteroatoms [21,22].…”

Manufacture of Carbon Materials with High Nitrogen Content

“…However, some authors have reported that the presence of nitrogen does favor CO 2 capture [ 6 , 7 ], but their synthetic method is completely different. Some authors have developed other types of strategies to generate carbons doped with nitrogen, basically using a ball mill, where they jointly grind a carbon precursor such as graphene oxide and melamine, also synthesize C 3 N 4 in a similar way, where they show that the new generated material ostensibly improves the catalytic properties in the ORR [ 8 , 9 , 10 ]. We can conclude that the presence of N is necessary, but only once what type of N is adequate for the capture to be more efficient has been determined.…”

Facile Modification of Flexible Electrodes via Laser Transfer

“…Metal acetylacetonates are compounds derived from the acetylacetonate anion and metal ions [ 1 ] and they are currently utilized in a plethora of applications, such as precursors for catalysis [ 2 ], for the development of hybrid nanomaterials or membranes with enhanced gas separation performance [ 3 ], in energy storage applications [ 4 , 5 ], in sensor designs [ 6 , 7 ], in oxygen reduction reaction [ 8 , 9 ] or in generation of hydrogen [ 10 ].…”