Enhanced Electromagnetic Energy Conversion in an Entropy-driven Dual-magnetic System for Superior Electromagnetic Wave Absorption

Thermochemical conversion is a highly effective method for upgrading organic solid wastes into high-value materials, contributing to carbon neutrality and peak, carbon emission goals. It also serves as a pathway to develop energy-efficient electromagnetic wave absorbing (EMWA) materials. In this study, fish skin to successfully in situ nitrify Prussian Blue into Fe3N under external thermal driving condition, resulting in high saturation magnetization is utilized. The resulting Fe3N@C demonstrates outstanding EMWA property, achieving a minimum reflection loss of -71.3 dB. Furthermore, by introducing cellulose nanofiber, a portion of the iron nitride is transformed into iron carbide, resulting in Fe3C/Fe3N@C. This composite exhibits enhanced EMWA properties owing to wider local charge redistribution and stronger electronic interactions, achieving an effective absorption bandwidth (EAB) of 6.64 GHz. Electromagnetic simulations and first-principles calculations further elucidate the EMWA mechanism, and the maximum reduction value of the radar-cross section reached 37.34 dB.m(2.) The design of multilayer gradient metamaterials demonstrated an ultra-broadband EAB of 11.78 GHz. This paper presents an efficient strategy for atomic-level biomass waste utilization to prepare Fe3N, provides novel insights into the conversion between metal nitrides and metal carbides, and offers a promising direction for the development of advanced EMWA materials.