Graphene oxide/carbon nanotube reinforced PCM microcapsules with high thermal conductivity and high latent heat for thermal energy storage

Efficient thermal energy storage requires phase change materials (PCMs) with both high latent heat and enhanced thermal conductivity. Here, polymethyl methacrylate (PMMA)-based PCM microcapsules were synthesized <i>via</i> emulsion polymerization with interfacial self-assembly, incorporating graphene oxide (GO) and carbon nanotubes (CNTs) as conductive fillers. Optimization of emulsifier type and shell-to-core ratio improved morphology and encapsulation, with a 0.50 ratio achieving 67.7% high loading and latent heat exceeding 165 J g^-1. Comprehensive characterization (FTIR, Raman, XRD, XPS) confirmed strong interfacial interactions between fillers and polymer shells. The combined addition of GO and CNTs reduced leakage, increased latent heat retention by over 12%, and yielded uniform capsule morphology. Infrared thermal imaging further revealed that PCM-GO/CNTs microcapsules exhibited slower cooling, more stable temperature plateaus, and superior heat storage performance compared with control and single-filler systems. These findings highlight the effectiveness of hybrid GO/CNT incorporation in enhancing both structural stability and thermal regulation, offering a promising route for advanced thermal energy storage applications.