Multifunctional phase change composites enabled by structurally engineered carbon microtubule aerogels for efficient thermal energy conversion and storage

Abstract

The development of sustainable phase change composites that simultaneously integrate high energy density, enhanced thermal conductivity, superior shape stability, excellent thermal management, and efficient multi-field driven energy conversion capability represents a fundamental scientific challenge. This work introduces a novel cobalt nanosheet (CoNS)-engineered carbonized kapok fiber (CKF) aerogel derived from renewable biomass for encapsulating lauric acid (LA), creating a multifunctional LA/CKF@CoNS phase change composite with unprecedented thermal energy storage performance. The CKF@CoNS architecture is fabricated through surface modification of kapok fiber, homogeneous Co(OH)₂ deposition, and controlled carbonization, yielding CKF microtubules conformally coated with interconnected metallic CoNS that form dual thermal–electrical networks while catalyzing CKF graphitization. The optimized LA/CKF@CoNS-5 composite delivers unprecedented latent heat retention (92.7% of pure LA) and thermal conductivity enhancement (480% of pure LA), along with superb shape stability and long-term reliability (2000 cycles). Notably, this PCC simultaneously achieves a photothermal conversion efficiency of 91.9% at 1000 W m⁻² and an electrothermal conversion efficiency of 96% at 3 W without supplementary fillers, enabled by the structurally engineered CKF@CoNS framework. The unique convergence of high energy density, efficient thermal transport, shape stability, and dual-energy conversion within a single filler-free system positions this CKF@CoNS-based composite as a promising candidate for electronics thermal management, solar energy storage, personal thermal wearables, and intelligent buildings. Leveraging renewable biomass, the in situ metallic nanosheet growth methodology establishes a scalable strategy overcoming key limitations in PCCs, and further opens avenues for sustainable multifunctional material design.