3D-architected carbon microtubule aerogel based phase change composite for multi-field-responsive high-efficiency energy conversion

Phase change materials (PCMs) are pivotal for advanced thermal energy management and energy utilization systems, yet simultaneously balancing high latent heat, enhanced thermal conductivity, and multi-field-responsive thermal energy conversion capability in composite PCMs remains challenging. This study pioneers a carbon microtubule aerogel (CMA)-based composite PCM (CMAPCM) engineered from cobalt nanocatalyzed carbonized kapok fibers (CKF@CoNP), demonstrating unprecedented thermophysical performance. The hierarchically structured CKF@CoNP framework-featuring 3D interconnected carbon microtubules and catalytic CoNP sites-enables the synergistic enhancement in energy density, photon/electron transport, and multi-field responsiveness for the novel CMAPCM. The optimized CMAPCM-10/20/30 variants exhibit record high specific latent heats of 206.7–196.8 J/g (vs. 194.1 J/g for pristine PCM), alongside tunable thermal conductivity (0.66–0.94 W/m·K) with CMA content below 1.2 wt%. The highlighted CMAPCM-20 as the optimal candidate, exhibits solar-thermal conversion efficiencies of 0.73, 0.91, and 0.97 under solar intensities of 0.7, 1.0, and 1.4 sun, respectively, coupled with a solar-thermoelectric conversion efficiency of 0.51 when paired with thermoelectric generators. Additionally, it achieves electrothermal conversion efficiencies of 0.61, 0.91, and 0.94 at 0.5, 1.0, and 1.5 W inputs. The composite maintains its latent heat capacity well after 2000 thermal cycles, confirming structural stability. By unifying the ultrahigh latent heat capacity, tunable thermal conductivity, and multi-field energy conversion in a single material system, this work establishes a versatile platform for solar-thermal systems, off-peak electricity storage, smart thermal management, and infrared/electromagnetic compatibility applications.