Upgrading of silicon slag into radiative cooling materials by controlled oxidation with oxygen carriers

Abstract

Energy saving and waste recycling are two important factors for sustainability of the Earth. Radiative cooling is an effective technology for decreasing cooling energy consumption. Realization of the low-cost preparation of radiative cooling materials is key to large-scale applications but is still challenging. Meanwhile, the growing prosperity of the metallurgical industry has led to abundant silicon-containing solid wastes. In this work, for the first time, an upgrading strategy to transform silicon-containing solid wastes into radiative cooling materials is proposed using silicon slag as a representative raw material. To eliminate the SiC component, which demonstrates strong sunlight absorption and high chemical inertness, an oxygen carrier (CeO_x or SrO_x)-assisted accelerated oxidation strategy is developed. Al is introduced to modify the crystal structure of the products to improve the radiative cooling performance. Blended with poly(4-methyl-pentene), a membrane with a CeO_x-assisted annealed product (A-SiS-Al/Ce) shows a radiative cooling power of 67.3 W m⁻². In contrast, a silicon slag membrane shows a sunlight heating power of 68.5 W m⁻² due to sunlight absorption by the Si and SiC components. Energy consumption simulation indicates that the A-SiS-Al/Ce membrane can efficiently save cooling energy in wide regions with climatic parameters of temperate, hot summer with cold winter, and hot summer with warm winter.