High thermal conductivity biomass-derived carbon by K2FeO4 activation for thermal energy storage

Solid-liquid phase change materials (PCMs) possess green and reversible thermal storage characteristics, but their application is limited by liquid leakage in the molten state and the low thermal conductivity of solid-liquid PCMs. Biochar (BC), with its inherent porous architecture and abundant surface functionalities, was synthesized through K2FeO4 activated carbonization of straw, a representative agricultural residue, demonstrating exceptional potential as a sustainable matrix material. After loading polyethylene glycol, the composite PCMs were obtained (BC/PEG). The research focused on investigating the effects of carbonization temperature and K2FeO4 on the structural properties of biochar. The results indicated that when the carbonization temperature is 800 °C and the proportion of K2FeO4 is 1:1, the specific surface area of BC reaches 1463.85 m2/g. The BC/PEG has excellent heat storage performance, with a loading rate as high as 74.8% and a melting enthalpy of 120.7 J/g. While maintaining a high loading rate, BC/PEG800-1 exhibited a thermal conductivity of 0.449 W/(m·K), representing a 38.6% enhancement over that of pure PEG. The findings suggest that biochar derived from K2FeO4 activated biomass effectively addresses PCM leakage and low thermal conductivity. This material exhibits promising potential for energy storage systems, offering a novel strategy to enhance thermal performance in PCMs.