Temperature-modulated surface features of neem seed biochar for sustainable thermal energy storage applications

Abstract Addressing the surging global energy demand while mitigating environmental degradation necessitates a paradigm shift from conventional energy systems to sustainable alternatives. However, the inherent intermittency of renewable energy sources mandates efficient harvesting mechanisms and advanced storage technologies to ensure uninterrupted energy availability. Thus, optimizing energy generation and storage systems is imperative for maximizing renewable energy utilization and advancing carbon neutrality. Biochar-based phase change materials (PCMs) emerge as a viable solution, simultaneously enhancing thermal energy storage efficiency and contributing to carbon sequestration. This study synthesizes biochar-based PCM composites using Neem (Azadirachta indica) seed-derived biochar, produced at two distinct pyrolysis temperatures (300 °C and 500 °C), and impregnated with lauric acid (LA). Comprehensive characterization through BET surface area analysis, FT-IR spectroscopy, SEM–EDS, DSC, and TGA evaluated the structural, chemical, and thermal properties of the composites. The biochar pyrolyzed at 500 °C exhibits a significantly higher surface area (668 m 2 /g), facilitating enhanced PCM loading. FT-IR analysis confirmed the successful impregnation of LA while preserving its molecular structure, while SEM analysis revealed a highly porous biochar network that optimizes PCM accommodation. DSC and TGA results demonstrated an impressive latent heat storage capacity up to 94.92 J/g, stable phase transition behavior, and improved thermal stability. Leakage tests and infrared thermal imaging further validated the composites’ shape-stabilizing efficiency, ensuring controlled heat absorption and dissipation without PCM leakage. By utilizing waste biomass, this study presents a sustainable and cost-effective approach to advanced thermal management, contributing to enhanced energy conservation and a reduced carbon footprint. Graphical Abstract