Contrasting roles of CO2 activation and N2 pyrolysis in bamboo shoot shell carbon for thermal energy storage

Against the backdrop of escalating research on biomass-derived porous carbons for thermal energy storage, where the carbonization atmosphere profoundly dictates pore architecture and functional performance. This study systematically investigates the roles of CO 2 activation and N 2 pyrolysis in tailoring bamboo shoot shell (BSS)-derived porous carbons for polyethylene glycol (PEG)-based phase change materials (PCMs). CO 2 activation at 900 °C induced hierarchical porosity (specific surface area: 567.1 m 2 /g, average pore width: 2.17 nm), achieving a 60.47 % PEG encapsulation efficiency. However, the confined pore structure impeded PEG molecular mobility, increasing non-isothermal crystallization activation energy (ΔE a  = −160.16 kJ/mol) and prolonging half-crystallization time. In contrast, N 2 -pyrolyzed carbon (NCB) retained minimal porosity (15.2 m 2 /g) but higher graphitization, serving as efficient nucleation sites to reduce ΔE a (−153.44 kJ/mol) and enhance photothermal conversion efficiency (87.4 % compared to 85.6 % for CO 2 -activated composites). Both composites exhibited leak-proof stability and thermal cyclability. This innovation bridges waste-to-energy solutions with renewable energy technologies, expanding the applicability of PCM-based systems in solar thermal devices.