NO(x) degradation ability of S-g-C(3)N(4)/MgAl-CLDH nanocomposite and its potential application in cement-based materials

In this study a new photocatalytic nanocomposite, S-g-C(3)N(4)/MgAl-CLDH, was synthesized and implemented into cement mortar by internal mixing or coating. The photocatalytic NO(x) degradation efficiency of the S-g-C(3)N(4)/MgAl-CLDH and photocatalytic mortar was investigated. The NO(x) degradation efficiency and photoluminescence spectra of S-g-C(3)N(4)/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-C(3)N(4), the S-g-C(3)N(4)/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 NO(x) degradation rate of S-g-C(3)N(4)/MgAl-CLDH achieves 100% as compared to merely 81.5% of S-g-C(3)N(4). After being submerged in simulated concrete pore solution, the S-g-C(3)N(4)/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 NO(x) degradation ability of the internally mixed mortar is enhanced with an increase in the dosage of S-g-C(3)N(4)/MgAl-CLDH. For coated mortar, in contrast, a decline in NO(x) degradation rate is observed after 5 layers of coating owing to the lower porosity of mortar after excessive coating.