Prominently enhanced corrosive gas NO2 resistibility for silicone rubber composite coatings by incorporation of functional g-C3N4 nanosheets

In this study, the functional graphitic carbon nitride (g-C3N4) nanosheets are prepared to enhance the NO2 resistibility of room temperature vulcanized (RTV) silicone rubber. After corrosive gas NO2 oxidation for 24 h, the water barrier ability of RTV nanocomposite coatings was evaluated by electrochemical impedance spectroscopy (EIS). At the optimal filler content of 0.3 wt.%, the impedance module |Z| of functional g-C3N4/RTV is 3☓108 Ωcm2 with the best coating integrality, compared with 2☓107 Ωcm2 for the functional graphene oxide (f-GO)/RTV and 6.45☓106 Ωcm2 for the pure RTV silicone rubber. The microstructure evolution in nanocomposite was investigated by positron annihilation lifetime spectra (PALS). The results indicate that the functional g-C3N4 nanosheets improve the interfacial compatibility and reinforce the RTV matrix, which decrease the free volume for NO2 diffusion. The density functional theory (DFT) calculations reveal that the triazine structures in the g-C3N4 surface can effectively interact with NO2 molecules. Simultaneously, silanes grafting promotes exfoliation and good dispersity of g-C3N4. Due to highly decentralized two-dimensional functionalized g-C3N4 with high aspect ratios, the significant synergy effect between physical barrier and chemisorption is achieved.