Enhanced thermal conductivity of a superhydrophobic thermal energy storage coating based on artificially cultured diatom frustules

Solid-liquid phase change materials (PCMs) provide an eco-friendly and cost-effective solution for waste heat recovery and thermal management. However, leakage and low thermal conductivity are two long-standing bottlenecks for their large-scale application. Applying a synthesized multi-level porous scaffold to prepare shape-stabilized PCMs (ss-PCMs) is an efficient, but high-cost strategy used to address the above problem. Herein, a strategy for fabricating enhanced thermally conductive ss-PCM coatings has been developed using artificially cultured, hierarchically porous Ag nanoparticle decorated diatom frustules (Ag-DFs) utilizing a facile spray-coating method. The delicate pores and high specific surface area (101.78 m2/g) endow the Ag-DFs to adsorb 55 wt% of paraffin wax (PW) without leakage, thereby exhibiting a melting enthalpy of 114.27 J/g. The corresponding ss-PCM coatings demonstrate a thermal conductivity of 0.87 W/m·K, which is ∼ 2.95-fold higher than pure PW. In addition, the abundant micro/nanoscale texture in the Ag-DFs along with the low-surface-energy of PW synergistically produce superhydrophobicity in the coating, thereby improving its ability to resist external environmental impacts, extending the service life. With high energy storage density, enhanced thermal conductivity, and good scalability, our superhydrophobic ss-PCM coating should find potential use in energy-saving building materials and thermal management of electrical devices, as well as self-cleaning surfaces.