Preparation and characterization of bifunctional wolfsbane-like magnetic FeO nanoparticles-decorated lignin-based carbon nanofibers composites for electromagnetic wave absorption and electrochemical energy storage.

Recently, with the pursuit of high-efficiency electromagnetic wave absorption (EMWA) and electrochemical energy storage (EES) materials, multifunctional lignin-based composites have attracted significant interest due to their low cost, vast availability, and sustainability. In this work, lignin-based carbon nanofibers (LCNFs) was first prepared by electrospinning, pre-oxidation and carbonization processes. Then, different content of magnetic FeO nanoparticles were deposited on the surface of LCNFs via the facile hydrothermal way to produce a series of bifunctional wolfsbane-like LCNFs/FeO composites. Among them, the synthesized optimal sample (using 12 mmol of FeCl·6HO named as LCNFs/FeO-2) displayed excellent EMWA ability. When the minimum reflection loss (RL) value achieved -44.98 dB at 6.01 GHz with an thickness of 1.5 mm, and the effective absorption bandwidth (EAB) was up to 4.19 GHz ranging from 5.10 to 7.21 GHz. For supercapacitor electrode, the highest specific capacitance of LCNFs/FeO-2 reached 538.7 F/g at the current density of 1 A/g, and the capacitance retention remained at 80.3 %. Moreover, an electric double layer capacitor of LCNFs/FeO-2//LCNFs/FeO-2 also showed a remarkable power density of 7755.29 W/kg, outstanding energy density of 36.62 Wh/kg and high cycle stability (96.89 % after 5000 cycles). In short, the construction of this multifunctional lignin-based composites has potential applications in electromagnetic wave (EMW) absorbers and supercapacitor electrodes.