Passive daytime radiative cooling inorganic-polymeric composite artificial lawn for the alternative to the natural lawn

The natural lawn needs complex maintenance (e.g., fertilizer dressing, manicuring, soil disinfection and disinsection), so the artificial lawn is increasingly desired and applied in the sports arena. However, the most artificial lawns are made of the organic materials, which could accumulate the thermal energy under direct sunlight. The accumulated thermal energy also leads to increasing the temperature of the artificial lawn and its surroundings, which eventually impact the athletic experience. Moreover, an efficient, eco-friendly, and economical technique that can provide the cooling for the artificial lawns without extensive energy input is lacking. Herein, a novel inorganic-polymeric composite for preparing passive daytime radiative cooling artificial lawn using chromium oxide (Cr₂O₃) particle-embedded high-density polyethylene (HDPE) is demonstrated. By reflecting 50% NIR irradiance and radiating heat through the atmosphere's long-wave infrared transmission window (LWIR, ε_LWIR = 0.86), this composite-covered device displayed a temperature of 30.7 °C, much lower than those of HDPE-covered device (43.4 °C) under solar simulator (intensity~0.34 W/cm²). Similarly, this composite exhibits a better cooling effect than the neat HDPE under direct sunlight. Moreover, for further improving the cooling property of the composite, the titanium dioxide (TiO₂) was utilized to enhance the reflectance of the HDPE/Cr₂O₃ composite without affecting the visual effect and thermal emissivity, where the total reflectance increases by 5%. Meanwhile, the outdoor thermal measurement showed that the cooling effect of the HDPE/Cr₂O₃/TiO₂ composite artificial lawn is on a par with that of the natural lawn.