High thermal storage ability and photothermal conversion capacity phase change capsule with graphene oxide covalently grafted silica shell

Abstract

Preparation of phase change materials with energy collection, conversion and storage functions is considered to be an important way to solve the energy shortage problem. Hence, a novel phase change capsule (EP@MGO) with photothermal conversion function was innovatively designed. In the process of preparing EP@MGO, the modified graphene oxide (MGO) layer was covalently anchored on the surface of the phase change capsule encapsulated by silica shell (EP) through Si-O-Si bonds, in which MGO was obtained by modifying GO nanosheets with isocyanate propyl triethoxysilane. The as-prepared EP@MGO microcapsule presents favorable latent heat storage capacity, with enthalpy of 139.8 J/g and high encapsulation efficiency of 83.6%. Besides, the thermal stability, leakage-proof property, durability, and thermal reliability of EP@MGO were enhanced significantly due to the physical protection effect provided by the SiO2-MGO double-layer shell. Moreover, the covalently MGO-grafted silica shell endows EP@MGO with high thermal conductivity (1.603 W/m·K), which improves its thermal management efficiency. More importantly, EP@MGO exhibits the potential ability to effectively utilize ultraviolet and visible light. In detail, the absorbance of EP@MGO increased by ∼192% in the ultraviolet and visible light region (200–800 nm), and the photothermal conversion efficiency under near infrared (NIR) region as high as 64.4%, which has negligible change (64.2%) even after 50 times heating-cooling cycle. Therefore, the phase change capsule EP@MGO provides a new idea for realizing efficient utilization of solar energy, and exhibits the application potential in biomedical treatment, smart textiles, and solar thermal collector.