Hypophosphite Tailored Graphitized Hierarchical Porous Biochar toward Highly Efficient Solar Thermal Energy Harvesting and Stable Storage/Release

Abstract Utilization of renewable solar energy is a promising pathway to relieve the severe energy shortage in current fossil fuel society, for which phase change materials (PCMs) based on sustainable porous biomass carbon materials represent an attractive and enormously potential option. However, structural tailor of hierarchical pores independent of biomass natural structure is still difficult for these carbon materials, thus seriously limiting their efficiency in solar thermal energy harvesting and stable storage/release. In this work, hierarchical porous carbons (HPCs) derived from chestnuts were fabricated by using aluminum hypophosphite (AP) as a multifunctional (dehydrating, blowing, and crosslinking) activator. Different measurements confirmed that unique interpenetrating HPC network structures with continuous channels were tailored via the triple effects of AP. The resulting HPC displays high pore volume and high thermal conductivity. The HPC-stabilized composite PCM with 85 wt% octadecane (Octadecane85@HPC) possesses the high transition enthalpy of 216.2 J g-1 and shows high reliability in thermal cycle test. Compared with currently reported similar bio-based PCMs, the Octadecane85@HPC shows higher energy storage capacity. Interestingly, the solar thermal energy conversion efficiency of the Octadecane85@HPC reaches 96.1%, presenting excellent solar energy harvesting capacity. This work provides a promising strategy to tailor biomass HPC for highly efficient solar thermal energy harvesting and storage/release.