Graphitic (g)-CxNyHz has become a popular family of photoharvesters in photocatalytic water splitting cells, as well as other applications in chemistry. In this Article, different g-CxNyHz structures were studied thermochemically using DFT. Following a benchmark study with different families of functionals, the B3LYP functional was shown to accurately capture the thermochemistry of carbon nitride synthesis. A triple-ζ polarized basis set, in combination with Civalleri’s modification to Grimme’s D2 formalism (with s6 = 0.5) for dispersion interactions, yielded accurate geometries. Grimme’s D3 formalism with Becke–Johnson damping was used to refine the energetic description of dispersion interactions. The stepwise cycloaddition of cyanamide to form melamine was shown to be exergonic, whereas the stepwise deamination of melamine to form g-C3N4 was shown to be endergonic. Of those structures respecting the [C6N9H3]n chemical formula, the structure commonly known as “melon” was found to be most stable, whereas the sp3-hybridized [C6N9H3]n elucidated by Horvath-Bordon et al. was found to be the least stable. Fully polymerized triazine-based g-C3N4 appeared slightly more stable than heptazine-based g-C3N4.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): KAUST 1974-02
Acknowledgements: Funding for this work was provided by the King Abdullah University of Science and Technology (KAUST), within the framework of Special Academic Partnership Program “Water Splitting” (projects ENSL 14.065 and KAUST 1974-02). We gratefully acknowledge the computational resources provided by l’Institut du Développement et des Ressources en Informatique Scientifique (IDRIS, under project x2015080609) of the Centre National de la Recherche Scientifique (CNRS) and by the Pôle Scientifique de Modélisation Numérique (PSMN) at ENS Lyon. S.T.A.G.M. thanks Dr. R. Grüber (ENSL) and Prof. T. Maschmeyer’s Carbon Nitride team (Sydney University) for fruitful discussions.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.