Functional Modification Of Cellulose Aerogel And Its Mechanism Of Enhancing The Performance Of Phase Change Energy Storage Material

Cellulose aerogel(CA)was an ideal encapsulation carrier for solid-liquid phase change materials due to its advantages of ultra-high porosity,ultra-low density and high specific surface area.In this paper,the functional modification of CA has effectively solved the problems of limited latent heat,low thermal conductivity,low photothermal conversion efficiency and poor mechanical strength in the application process of CAbased composite phase change materials.In this paper,a one-step in-situ encapsulation method was designed to prepare CAbased composite phase change materials PCD-X based on freeze casting technology.The encapsulation of polyethylene glycol(PEG)and CA modification were completed during the CA formation,achieving a high encapsulation efficiency(95 wt%)and high latent heat release to PEG.Importantly,a weaker hydrogen bonding mode(O-H···O before modification > O-H···N or N-H···O after modification)was constructed for CA and PEG,which effectively weakened the "non-phase-change layer" of CA-based composite phase change materials,making the heat storage capacity of PCD-X close to the theoretical value,as high as ～194.3 J/g(modification increase ratio ～18.9%).which effectively solves the problem of limited latent heat of CA-based composite phase change materials.Introducing MXene to functionalize the CA structure,a MXene/cellulose aerogelbased composite phase change material PMC-X was constructed in situ,which effectively improved the thermal conductivity of the CA-based composite phase change material(～0.40 W/m K)and photothermal conversion performance(～91.6 %).Importantly,through the rational structural design between MXene,PEG and cellulose,the heat storage capacity of PMC-X did not decrease significantly(about 183 J/g)after the introduction of MXene,but the strength was only 0.153 MPa.The influence mechanism of MXene and aerogel network structure on the thermal conductivity and photothermal conversion efficiency of PMC-X was explored,and a CA-based composite phase change material with high thermal conductivity,efficient photothermal conversion,and high latent heat release was constructed.By functionalizing the CA structure with polyvinyl alcohol,borax,and MXene,a one-step in situ construction with high toughness(tensile strength ～3.286 MPa),high thermal conductivity(0.71 W/m K)and high photothermal conversion efficiency was constructed.The paraffin-cellulose/MXene/polyvinyl alcohol/borax aerogel-based composite phase change film PCMPD-X effectively improves the problems of low mechanical strength and low thermal conductivity of CA-based composite phase change materials,and solves the problem of paraffin wax Due to the problem of limited latent heat in the dense pore structure,the effect mechanism of the crosslinking of polyvinyl alcohol and borax on the phase transition behavior,thermal conductivity and mechanical strength of PCMPD-X was explored.In this paper,the functional modification of CA and its mechanism of enhancing the performance of phase change energy storage materials were systematically carried out..It provides new research ideas and approaches for the design of CA-based composite phase change materials with high heat storage capacity,high heat storage efficiency,high photothermal conversion,and high mechanical properties,and is expected to provide technical support and theoretical basis for the application of CAbased composite phase change materials.