The exploitation of from-stable phase change materials (PCMs) with superior energy storage capacity and excellent solar−thermal conversion performance is crucial for the efficient exploitation of solar energy. Herein, 2D-layered polymerized dopamine-decorated Ti 3 C 2 T x MXene nanosheets (P-MXene) with superior photothermal effects and excellent oxidation stability were synthesized from Ti 3 AlC 2 particles by the selective etching and self-polymerization of dopamine. Then, novel biomass-derived PCM composites, eMPCMs, were fabricated by impregnating erythritol into P-MXene/cellulose nanofiber (CNF) hybrid aerogels. The porous and interconnected 3D aerogels adequately support erythritol and resist liquid leakage during thermal storage. Differential scanning calorimetry (DSC) results showed that the eMPCMs based on P-MXene/CNF aerogels exhibited an extremely high thermal storage density (325.4−330.6 J/g) and excellent PCM loading capacity (up to 1929%). The introduction of P-MXene nanosheets into eMPCMs significantly increased the solar−thermal conversion and storage efficiency, solar−thermal−electricity conversion capacity, and thermal conductivity of the synthesized PCM composites. Moreover, the P-MXene/CNF hybrid aerogelbased PCM composites possessed excellent long-term thermal reliability and thermostability. Hence, the synthesized eMPCMs reveal tremendous potential for efficient solar−thermal storage fields.

In order to efficiently exploit solar-thermal energy, it is essential to develop form-stable phase-change material (PCM) composites simultaneously with superior solar-thermal storage efficiency, excellent flame retardancy, and improved thermal conductivity. Herein, phytic acid (PA)-modified, zinc oxide-deposited, and surface-carbonized delignified woods (PZCDWs) were constructed by alkaline boiling, PA modification, ZnO deposition, and surface carbonization. Then, novel form-stable PCMs (PZPCMs) with superior solar-thermal storage efficiency, excellent flame retardancy, and improved thermal conductivity were fabricated by impregnating n-docosane into PZCDWs under vacuum. The PZCDW aerogels can well support the n-docosane and overcome liquid leakage owing to their superior surface tension and strong capillary force. Differential scanning calorimetry results showed that PZPCMs possessed superior n-docosane encapsulation yield and high phase-change enthalpy (185.2–213.1 J/g). Decorating delignified wood by surface carbonization and ZnO deposition significantly improved the solar-thermal conversion efficiency (up to 86.2%) and thermal conductivity (193.3% increased) of PCM composites. Furthermore, with the introduction of PA into PZPCMs, the peak heat release rate and total heat release of the PCM composites decreased considerably, indicating the enhanced flame retardancy of PZPCMs. In conclusion, the novel renewable wood-based PCM composites demonstrate promising potential in solar energy harnessing and thermal modulation technologies.

The development of form-stable phase change materials (PCMs) with flame retardancy and the visual thermal storage process is crucial for their application in building energy conservation. Herein, an active phosphorus/ammonium-containing non-formaldehyde flame retardant (APA) was synthesized based on the natural compound phytic acid. Then, wood-based form-stable PCM composites (PTPCMs) with high energy storage density, excellent flame retardancy, and real-time and visual reversible thermochromic properties were successfully fabricated by impregnating the thermochromic compound into the APA-grafted delignified wood. The delignified wood well supports the solid–liquid PCMs and avoids their liquid leakage during phase transition due to the high surface tension and strong capillary effect. The differential scanning calorimetry (DSC) results showed that the PTPCMs possessed high thermal energy storage density (165.3–198.6 J/g) and reliable thermal stability. With the concentration of the flame-retardant APA increased, the peak heat release rate (pHRR) and total heat release (THR) of PTPCMs reduced noticeably, demonstrating the enhanced flame retardancy of PTPCMs. Moreover, PTPCM composites had good thermoregulation properties and the visualization of the phase transition process was made possible by the reversible thermochromic properties. In summary, the novel PTPCMs show tremendous application potential for efficient building energy conservation.

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Impregnating organic phase-change materials (PCMs) into biomass-derived aerogels is regarded as one of the most effective and accessible approach to address the liquid leakage issues of solid–liquid PCMs. However, the inefficient solar–thermal conversion and low thermal conductivity still restrict the large-scaled applications of organic PCMs in solar utilization fields. Herein, novel form-stable PCM composites (CMPCM-Fe) with enhanced thermal conductivity and excellent solar- and magnetic-driven thermal energy conversion and storage efficiency were fabricated by impregnating n-docosane into Fe3O4-functionalized κ-carrageenan/melanin hybrid aerogels (CMA-Fe) through vacuum impregnation. CMA-Fe effectively supported n-docosane and prevented the leakage issue during the phase transition process owing to its strong surface tension and capillary force. CMPCM-Fe exhibited high encapsulated efficiency (88.9–94.6%), satisfactory thermal storage capacity (229.1–246.9 J/g), and excellent reversible stability. The introduction of Fe3O4 nanoparticles enhanced the thermal conductivity (55.3% increased) and solar–thermal conversion efficiency (up to 93.5%) of CMPCM-Fe and endowed it with excellent magnetic–thermal conversion capacity under an alternating magnetic field. The synthesized CMPCM-Fe possesses broad application prospect in mutiresponse thermal management.