A novel metal-free fluorine-free self-cleaning coating with photocatalytic activity and superhydrophobicity based on RP/HTCC@PDMS for hydraulic concrete

Abstract

Hydraulic concrete structures, frequently exposed to water environments, are highly susceptible to surface contamination by inorganic solid particles, organic chemical pollutants, and microorganisms like algae. In response, a novel metal-free fluorine-free coating was developed by combining red phosphorus/hydrothermal carbonization carbon (RP/HTCC) and polydimethylsiloxane (PDMS) with photocatalytic activity and superhydrophobicity to enable superior self-cleaning for hydraulic concrete. The proper integration of HTCC into RP (RP/HTCC-2) introduced a micro-nanostructured surface, improved light absorption, optimized band energy alignment, and enhanced photogenerated charge separation and migration. Correspondingly, the RP/HTCC-2@PDMS coating exhibited good self-cleaning for organic pollutant degradation on concrete surfaces, achieving 97.6 % for Rhodamine B (RhB) and 82.5 % for tetracycline hydrochloride (TCH) in water within 4-h visible light irradiation. Meanwhile, it showed remarkable superhydrophobicity, with a high water contact angle (WCA) of 157 ± 0.5° and a low water sliding angle (WSA) of 6 ± 0.5°, driving efficient self-cleaning against powder dusts. Besides, RP/HTCC-2@PDMS demonstrated robust durability against high-intensity long-term UV exposure and water-jet impact. Furthermore, the synergistic effect of photocatalytic activity and superhydrophobicity were further evident in the coating’s algal antifouling and inhibition. After 12-h visible light irradiation, the RP/HTCC-2@PDMS coating achieved a 69.8 % reduction in Microcystis aeruginosa in water. Detailed analysis of the inhibition mechanism revealed significant changes in superoxide dismutase (SOD) activity, catalase (CAT) activity, malondialdehyde (MDA) content, phycobiliprotein (PB) content, and algae organic matters (AOM). Collectively, these findings are believed to provide valuable insights on the development of green sustainable self-cleaning coating and the advanced synergistic mechanisms driving their effective and robust self-cleaning.