Facile fabrication of densely packed ammoniated alumina/MXene/bacterial cellulose composite films for enhancing thermal conductivity and photothermal conversion performance

The full arrival of 5G and advances in electronic integration make efficient heat dissipation crucial for stable operation and longer product lifespan. In this study, a vacuum-assisted filtration process was employed to fabricate ammoniated alumina/MXene/bacterial cellulose (Al2O3-NH2/MXene/BC) composite films that display a unique integration of properties, encompassing ultra-high thermal conductivity (λ), mechanical flexibility, and high photothermal conversion performance. By leveraging the bridging effect among spherical Al2O3-NH2 and MXene nanosheets, a densely packed "point-surface" structure was constructed in BC by using a one-step preparation process. When the mass fraction of Al2O3-NH2/MXene (1:3, w/w) is 40 wt%, the O-BAl1M3 exhibited an in-plane λ of 20.02 W m–1 K–1, which was 436% and 94% higher than that of pure BC and T-BAl1M3 (prepared by a two-step method), respectively. Furthermore, constructing an intact thermal conductive network within BC notably promoted photothermal and photoelectric conversion performance. The maximum surface temperature and voltage of the O-BAl1M3 film reached 106.9°C and 48.34 mV when a sample with an area of 1.56 cm2 was exposed under a light intensity of 200 mW cm–2. By applying O-BAl1M3 film, the temperature inside a self-built greenhouse model reached up to 64.8°C within 1200 s under a light intensity of 100 mW cm–2, which validated the practical application of the composite films and offered a novel approach for creating flexible films with superior photothermal conversion capability. This work provided insights into preparing functional composite films for efficient thermal management and photothermal conversion applications.