Three-dimensional Porous Framework Lignin-Derived Carbon/ZnO Composite Fabricated by a Facile Electrostatic Self-Assembly Showing Good Stability for High-Performance Supercapacitors

This work demonstrates a kind of lignin-derived carbon/zinc oxide (LDC/ZnO) composite prepared through a facile electrostatic self-assembling carbonization process. Solidification of the lignin/zinc oxalate precursor results in zinc oxalate (ZnC2O4) crystalizing in lignin. The crystalized ZnC2O4 particle acts as both catalysts and activators during the high-temperature carbonization process. The prepared LDC/ZnO composites show a unique 3D porous framework structure, where ZnO nanoparticles are enchased by the lignin-derived carbon nanosheets. The LDC/ZnO composites show a high pore volume, large specific surface area, and high electrical conductivity, thus demonstrating excellent electrochemical properties. LDC/ZnO-700 displays a high gravimetric capacitance (193 F·g–1 at 0.5 A·g–1), outstanding durability, and superior rate capability in a two-electrode system using the polyvinyl alcohol/KOH gel as the electrolyte. The capacitance is still maintained as 161 F g–1 at 2.0 A·g–1 after 10 000 cycles. This article provides a simple approach for preparing a lignin-derived carbon composite for energy storage and also a new way for lignin valorization.