Préparation de matériaux à base de g-C3N4 et caractérisations analytiques pour des applications environnementales

Carbonitride with a graphitic structure (g-C3N4) is a promising material for photocatalysis. Its properties can be improved by heterojunction engineering, in which it is coupled with another material such as a metal or a semiconductor. In this thesis, the objective is to design nanocomposites based on g-C3N4 and carbon through an original process which allows to control the properties of these materials. These will be evaluated using physico-chemical and photocatalytic methods. For this, we synthesized CNx type materials in a wide composition range (0.66<x<1.4) by the adduct method based on the self-assembly between melamine (traditional source of g-C3N4) and a polycarboxylic acid (additional source of C). The physicochemical characterizations carried out after carbonization of the adducts, have made it possible to better understand the structuring of these CNx materials, which can be described by planes of the g-C3N4 structure in which nanodomains (or clusters) of the graphitic carbon type are dispersed. The chemical reactivity of these gC3N4/C nanocomposites was studied with oxygen (at high temperature 450-650°C) and with pure F2 (25°C) in order to better understand their structuring of these nanocomposites and to obtain new materials with potentially interesting photocatalytic properties. The thermal stability of these g-C3N4/C nanocomposites and derived materials obtained by reaction with F2 was investigated. In parallel, the possible photocatalytic applications of these different materials have been explored.Le carbonitrure de structure graphitique (g-C3N4) est un matériau prometteur pour la photocatalyse. En jouant sur l'ingénierie d'hétérojonction par un couplage avec un autre matériau de type métal ou semiconducteur, ses propriétés peuvent être améliorées. Dans cette thèse, l'objectif est de concevoir des nanocomposites à base de g-C3N4 et de carbone par un procédé original permettant de contrôler les caractéristiques de ces matériaux. Ces dernières seront évaluées grâce à des méthodes physicochimiques et photocatalytiques. Pour cela, nous avons synthétisé des matériaux de type CNx dans une large gamme de composition (0.66<x