NO_x degradation ability of S-g-C₃N₄/MgAl-CLDH nanocomposite and its potential application in cement-based materials

In this study a new photocatalytic nanocomposite, S-g-C3N4/MgAl-CLDH, was synthesized and implemented into cement mortar by internal mixing or coating. The photocatalytic NOx degradation efficiency of the S-g-C3N4/MgAl-CLDH and photocatalytic mortar was investigated. The NOx degradation efficiency and photoluminescence spectra of S-g-C3N4/MgAl-CLDH after being immersed in the simulated concrete pore solution were evaluated to assess its chemical stability. The results show that compared with S-g-C3N4, the S-g-C3N4/MgAl-CLDH exhibits a narrower bandgap (2.45 eV), a lower photogenerated electron-hole pair recombination rate and a higher specific surface area (36.86 m(2) g(-1)). After 21 min of visible light irradiation, the NOx degradation rate of S-g-C3N4/MgAl-CLDH achieves 100% as compared to merely 81.5% of S-g-C3N4. After being submerged in simulated concrete pore solution, the S-g-C3N4/MgAl-CLDH exhibits only a slight decrease of 5% in degradation rate after 12 min of irradiation, confirming a good compatibility and stability in cement-based materials. The NOx degradation ability of the internally mixed mortar is enhanced with an increase in the dosage of S-g-C3N4/MgAl-CLDH. For coated mortar, in contrast, a decline in NOx degradation rate is observed after 5 layers of coating owing to the lower porosity of mortar after excessive coating.