Multifunctional synergistic biomass-based composites: integrated design for energy conversion, electromagnetic shielding, and microwave absorption.

With the increasing complexity of precision electronic devices and the increasing demand for health-conscious solutions, it is crucial to design a multifunctional composite material that integrates thermal management and electromagnetic shielding. This study introduces a straightforward and sustainable method, utilizing renewable biomass resources as a carbon source. Multi-metal particles are embedded within biochar through a chemical deposition method, creating a functionalized framework. This framework is then infused with binary eutectic phase change materials (PCMs), resulting in a composite that integrates energy conversion, electromagnetic shielding, and microwave absorption. The fabricated CPCMs exhibit high phase change enthalpy and mild operating temperatures. Specifically, FeCoC/BEPCM and ZnNiC/BEPCM demonstrate excellent photothermal conversion efficiencies (89.61% and 94.57%) and magnetothermal heating rates (4.6 °C/min and 7.8 °C/min). The composite's three-dimensional functionalized carbon skeleton enhances energy conversion and transport, while improving electromagnetic shielding and microwave absorption. Notably, the composites achieve EMI shielding effectiveness of 41.2 dB and 47.1 dB, with a minimum reflection loss of - 44.5 dB at 7.5 GHz, covering nearly the entire 2-18 GHz microwave spectrum. These results not only present a new direction for developing advanced electromagnetic shielding materials, but also open new opportunities for utilizing biomass resources in high-value applications.