Effect of dry-wet cycling on NOx degradation and sterilization properties of cement mortar with g-C3N4/CoAl-LDH

The influencing mechanism of dry-wet cycling on the NOx degradation and sterilization properties of photocatalytic cement mortar (PCM) with g-C3N4/CoAl-LDH was investigated through the optical properties, mineral composition of cement hydration products, pore characteristics and nitrogen (N) content. The results indicate that as the cycle number increases, the N content, band gap, Urbach energy, NOx degradation rate and sterilization rate exhibit periodic variations, while the peak intensity of CH (a cement hydration product) decreases gradually. After 10 cycles, PCM demonstrates the maximum Urbach energy, N content, NOx degradation and sterilization rate, as well as the minimum band gap. At this stage, the Urbach energy, N content, NOx degradation and sterilization rate of PCM with 1.0 % g-C3N4/CoAl-LDH increase by 16.2 %, 24.9 %, 15.4 % and 40.8 %, while the band gap and the CH peak intensity decrease by 5.4 % and 23.4 %, respectively. Although the NOx degradation and sterilization rates of PCM exhibit periodic fluctuations during the dry-wet cycling, both of them surpass those before the cycles, which shows the excellent photocatalytic durability of PCM. It is expected that this study not only presents a new perspective on evaluating the durability of PCM's photocatalytic property, but also provides an alternative approach for the design of new multifunctional nanocomposites in cementitious materials for environmental pollution control.