Supercooling suppression of microencapsulated capric acid-stearic acid eutectic via lignin-zein stabilized Pickering emulsion for highly efficient thermal energy storage

This study develops a fully biobased phase change material (PCM) by encapsulating capric acid-stearic acid eutectic (CSE) with a lignin-zein shell. It is driven by core-shell aggregation in Pickering emulsion during solvent exchange. Herein, the introduction of zein effectively promotes core-shell aggregation and stabilizes CSE Pickering emulsion. Consequently, CSE@lignin-zein capsules (zein/lignin: 10:90, w/w) achieve enhanced yield (up to 88.2 %) and encapsulation efficiency (up to 88.9 %) with a high melting enthalpy of 81.6 J g- 1 at 28.2 degrees C. Furthermore, the lignin-zein shell significantly reduces the interaction between fatty acids (core) and lignin (shell), inducing homogeneous crystallization of fatty acids core. As a result, it suppresses supercooled phase transition at-2.5 degrees C and exhibits excellent thermal reliability over 200 cycles. The thermal conductivity of CSE@lignin-zein capsules is increased from 0.26 to 0.41 W m- 1 K- 1 with only 0.6 wt% graphene oxide nanosheet coating. Overall, this work offers a green solution to produce biobased PCM with highly efficient energy storage. The underlying mechanism of shell-induced supercooling suppression is studied systematically.