Coupling bentonite-mediated crystallization regulation and MXene/TiN-enabled multiscale photothermal conversion network to construct efficient composite phase change materials

Cellulose aerogel-based composite phase change materials (CPCMs) offer a promising pathway to achieve solar-driven thermoelectric conversion, yet their performance is often hindered by intrinsic limitations in thermal conductivity, crystallization kinetics, and form-stability. Herein, we report an interfacially self-assembled bacterial cellulose (BC)/TiN/V 2 C aerogel designed to encapsulate a bentonite (BT)/polyethylene glycol (PEG) mixture (BTV-BP). The synergistic effect of heterogeneous nucleation sites provided by hydrogen bonding interactions and nanoscale confinement within the BT layers significantly reduces the nucleation energy barrier for PEG, thus increasing the crystallization rate by at least 100%. Besides, a unique fish-scale patterned structure and microencapsulated aggregates formed by BT/PEG intercalation collaboratively reduce the PEG leakage rate to only 1.81%. Additionally, thanks to the gradient size coupling distribution of V 2 C and TiN over the aerogel, the photothermal conversion efficiency of BTV-BP reaches 92.8%, and the thermal conductivity enhancement rate is up to 433%. Notably, the advanced applications in solar-thermoelectric generation of BTV-BP exhibit a stable power of 3 mW under 1.5-sun irradiation, which can sustain long-term operation of an LED panel even in darkness, along with excellent self-cleaning performance. This work provides new insight into utilizing cost-effective clay minerals to construct efficient and stable solar-driven aerogel-based CPCMs.