Hydrogen bond crosslinked MXene aerogel/polyethylene glycol composite phase change materials with superior stability and photothermal conversion performance

MXene aerogel based composite phase change materials exhibit great promise for solar thermal utilization, yet their mechanical strength and heat transfer property need to be further boosted. In this work, MXene/cellulose nanofibers (CNF)/poly(ethylene glycol) (PEG) composite phase change material (MCP) with robust and high thermal properties is successfully developed. MXene/CNF (MC) aerogels are constructed through CNF-assisted three-dimensional assembly of MXene nanosheets and incorporation of Al 3+ crosslinking, which afforded mechanical strength enhancement induced by metal ion coordination and hydrogen bonding interactions. With MC aerogel as the support framework, MCP has phase change enthalpy of no less than 167.1 J·g −1 , and the phase change enthalpy only decreases by 2.89 % after 500 cycles, showing high enthalpy and excellent thermal cycle stability. The electric field distribution of MXene during the photothermal conversion process is demonstrated by finite-difference time-domain (FDTD) simulation, which visually reveals the localized surface plasmon resonance effect of MXene. The highly vertically oriented 3D MXene framework effectively strengthens the directional heat transfer of the MCP, leading to the rapid completion of photothermal conversion and heat transfer processes, and thus realizing a photothermal conversion efficiency of more than 90 %. The MCP developed in this study is a valuable material for solar thermal energy storage in practical applications. • A robust MXene based framework is constructed via hydrogen bonding cross-linking. • MCP shows high phase change enthalpy of 167.1 J·g −1 and excellent thermal stability. • The photothermal conversion efficiency of MCP is more than 90 %. • The enhancement mechanism of photothermal conversion by directional heat transfer is revealed.