One‐Step Synthesis of Multifunctional Bacterial Cellulose Film‐Based Phase Change Materials with Cross‐Linked Network Structure for Solar–Thermal Energy Conversion, Storage, and Utilization

Abstract As one of the important directions of solar energy utilization, the construction of composite photothermal phase change materials (PCM) with reasonable network support and low leakage in the simple method is important to solve the transient availability of solar energy and achieve long‐lasting energy output. Here, a multifunctional silylated bacterial cellulose (BC)/hydroxylated carbon nanotube (HCNT)/polyethylene glycol (PEG) (SBTP) photothermal film‐based PCM with cross‐linked network structure is prepared by simple one‐step synthesis. The formation of the cross‐linked network structure achieves the enhancement of BC support network, prominent dispersion of HCNT and the direct introduction and perfect interlocking of PEG. Therefore, the optimal SBTP film exhibits high thermal enthalpy of 145.1 J g −1 , enthalpy efficiency of over 94%, robust shape stability and low leakage of <1.2%. It also displays high photothermal conversion of over 80 °C, photothermal storage of 394 s g −1 and excellent stability. Thus, it can demonstrate a maximum output voltage of 423 mV and high power density of 30.26 W m −2 under three solar irradiations when applied in the solar–thermal–electric energy conversion field. Meanwhile, it also can apply in the thermal management of solar cell and light‐emitting diode (LED) chip, and convert the waste heat into electricity, demonstrating multi‐scene application capability.