Alkali metal doped crystalline g-C₃N₄ with an enriched cyano group for visible-light photocatalytic degradation of methylamine

In this study, alkali-metal-doped crystalline g-C3N4 with an enriched cyano group was synthesized using the molten salt method and used for the visible-light photocatalytic degradation of methylamine (MA), a common organic amine compound with a low odor threshold. Different types and proportions of melting salts (Li, K, and Na) were added during secondary calcination to regulate the morphology, crystallinity, and surface defects of graphitic carbon nitride (g-C3N4). With molten salt treatment matched the melting point of the binary salt system, a cyano group and alkali metal co-doped crystalline g-C3N4 with a high surface area and good crystallinity were prepared. Co-decorating the alkali metal and cyano groups on crystalline g-C3N4 facilitated the adsorption of MA, realized an excellent photo-charge transfer efficiency, and generated more superoxide radicals. Compared with pristine g-C3N4 (PCN), the apparent rate constant of LiK15 : 5-CCN for the degradation of MA increased by 10.2 times and the degradation efficiency of 1000 ppm MA gas was 93.1% after 90 min of irradiation with visible light, whereas the degradation efficiency of PCN was 19.2%.