Stabilization of melon phase during the formation of g-C3N4 from melamine and its structure-property relationship towards photocatalytic degradation of dyes under sunlight

The structure-property relationship of various intermediates formed during the step-wise dwell-in thermal condensation of melamine to g-C 3 N 4 under a range of reaction temperatures such as 350, 400, 450 and 500 °C is investigated. Apart from the conventional intermediates such as melam and melem, the melon phase has been stabilized via dwell-in thermal condensation temperature at 450 °C. The properties of this melon phase are explored by comparing the characteristics of melam, melem and g-C 3 N 4 using structural, morphological and optical studies. Finally, the photocatalytic properties of all these structures (melam, melem, melon and g-C 3 N 4 ) have been investigated towards the degradation of dyes such as methylene blue (48, 56, 78 and 93%, respectively), rhodamine B (19, 36, 64 and 89%, respectively) and their mixtures (i.e. MB + RhB) under sunlight irradiation. From the obtained results, it is predicted that this melon phase may consist the modified-heptazine frameworks and more terminal-amine groups. Such features enable this melon phase to have appropriate band edge potentials, narrow band gap energy (~ 2.89, 2.80, 2.72 and 2.64 eV, respectively) with rapid charge separation abilities and thereby to have excellent optical and photocatalytic properties as compared to the other intermediates.