Photocatalytic NOx abatement and self-cleaning performance of cementitious composites with g-C3N4 nanosheets under visible light

The combination of photocatalyst with cementitious materials for air pollution abatement and self-cleaning has gained considerable attention. However, the most popularly used photocatalytic cementitious composites based on TiO₂ achieve the purification function under ultraviolet sunlight, significantly impeding a broader application of photocatalytic cementitious composites. Here, the photocatalytic cementitious composites were prepared by incorporating g-C₃N₄ nanosheets (CNNs) in Portland cement. With the increase of CNNs content, the photocatalytic NO_x abatement and self-cleaning performance was notably improved, while the micro-hardness of cementitious composites increased first and then decreased. Among the three mixing dosages (0.5%, 1% and 2% by weight of cement), the cementitious composite admixed with 2% CNNs showed the highest photocatalytic NO_x abatement efficiency of 227.3 μmol m⁻² h⁻¹, and could degrade the rhodamine B within 40 min under visible light. Additionally, its microscopic hardness was 5.4% higher than the one without CNNs, suggesting that a moderate amount of CNNs (below 2%) in cementitious composites was effective in achieving an improved photocatalytic depollution performance.