Enhancement in conduction loss induced by morphology engineering for excellent electromagnetic wave absorption

Understanding the microstructure-property relationship from the microscopic and macroscopic perspectives, instead of semi-empirical rules, can facilitate the design of microcosmic morphology to adjust the impedance matching and dielectric loss of the carbon-based materials, which are still lacking so far. In this study, a clear correlation between microstructure and conduction loss was revealed in agarose-derived carbon using a facile salt-etching strategy, in which ferric nitrate acted more as a morphology modifier for bulky carbon rather than a component regulator. Specifically, with the increasing amount of ferric nitrate, the original smooth bulky carbon was etched with caves, which gradually enlarged in size and depth and thus thinned in wall, and eventually transformed into a three-dimensional (3D) interconnected cellular structure, accompanied by a gradual increase in conductivity. Benefiting from the optimal impedance matching and strong conduction loss originating from the unique 3D cellular structure of agarose-derived carbon, AF-3 exhibited super-wide and strong absorption with an effective absorption bandwidth of 7.28 GHz (10.32–17.60 GHz, 2.9 mm) and a minimum reflection loss of −46.6 dB (15.6 GHz, 2.5 mm). This study establishes the relationship between microstructure, dielectric properties, and loss mechanism in carbon-based materials and also provides a new insight into the fine modulation of EMW-absorbing properties from morphological design.