Anisotropic MXene@polydopamine-\nand Dialdehyde Carboxymethyl\nCellulose-Modified Collagen Aerogel Supported Form-Stable Phase Change\nComposites for Light-To-Heat Conversion and Energy Storage

As a renewable alternative heat source, the inherently\nintermittent\nfeature of solar energy needs to be coordinated by reliable energy\nconversion and storage systems for utilizing the most abundant solar\nenergy. Phase change materials (PCMs) are supposed to be advanced\nmediums for storing a great deal of heat generated by solar light.\nHowever, PCMs cannot effectively absorb and utilize solar energy due\nto leakage, low photothermal conversion efficiency, and poor thermal\nconductivity. Herein, we developed a collagen-based aerogel modified\nby dialdehyde carboxymethyl cellulose and polydopamine-modified two-dimensional\ntransition-metal carbide/nitride (MXene@PDA) through bidirectional\nfreeze-drying technology for supporting PCMs, which exhibited anisotropy\nin structure and properties. In particular, the thermal conductivity\nof the aerogel was 0.0871 W/(m·K) in the axial direction and\n0.0504 W/(m·K) in the radial direction, demonstrating its anisotropic\nthermal insulation performance. Moreover, the final aerogel composite\nPCMs had been obtained via impregnating the obtained aerogel supporting\nmatrix into polyethylene glycol (PEG) and hydrophobic treatment of\npolydimethylsiloxane, which exhibited outstanding solar–thermal\nconversion ability, good thermal storage capacity, advanced leakage-proof\nproperty, and antifouling performance. The loading rate of PEG was\nas high as 92.2%, and the melting enthalpy was 132.6 J/g. Most importantly,\nthe water contact angle was evaluated to be 156.8°, indicating\nits superior antifouling performance. This material has intensive\napplication prospects in the fields of solar energy collection, conversion,\nand storage.