Effect of MOF derived hierarchical Co3O4/expanded graphite on thermal performance of stearic acid phase change material

A hierarchical porous structure of ZIF-67 (ZIF: zeolitic imidazolate framework) derived hollow porous Co3O4 on expanded graphite (EG) was synthesized, and dispersed in stearic acid (SA) to obtain a novel shape-stabilized phase change material (PCM) with excellent thermal conductivity. Co3O4/EG was prepared by calcination of the product of ZIF-67 in-situ deposit on EG. Co3O4/EG shows 3D interconnected network structure featuring abundant pores and large specific surface area, exhibits an efficient enhancement on the thermal properties of SA and excellent shape-stabilizing effect which prevents the leakage of molten SA. The obtained novel shaped-stabilized SA/Co3O4/EG composite PCM reveals remarkable thermal properties, which are superior to those of SA/EG, SA/Co3O4 and pure SA counterparts. The thermal conductivity of SA/Co3O4/EG-10 is 2.53 W·m−1·K−1 which is 7.67 times than that of pure SA. The high surface area and abundant hierarchical pore volume of Co3O4/EG additive could provide an effective hierarchical thermal transfer path for SA, and thus enhance the thermal properties of SA. This study will open an avenue to design and fabricate advanced PCMs for low-temperature solar energy storage.