(330e) Tailored Mesoporous Structures of Lignin-Derived Nano-Carbons for High Performance Supercapacitors

As a natural polymer with a high carbon to oxygen ratio, lignin is often considered a waste byproduct of pulp and biofuel production. Lignin’s random and complex heterogeneous structure poses a challenge to developing high-performance carbon materials. Nevertheless, previous work demonstrated promise using kraft lignin as a feedstock for carbon composites applications. This work presents an efficient one-step method to create highly mesoporous activated carbons from Kraft lignin. We achieved surface areas greater than 3,000 m² g^-1 and a mesopore ratio of 80% to develop electrodes in high-performance supercapacitors. For comparison, we also used a traditional two-step chemical activation method to produce activated carbons to elucidate the precursor-process-structure-performance relationship of lignin feedstocks resulting in enhanced electrochemical performance. One-step activation produced ACs with ultrahigh surface area and high mesopore ratio, leading to ultrahigh capacitance and energy density of the fabricated SCs. In comparison ACs, produced through two-step activation, have limited surface area but high oxygen content. The hydrophilicity of ACs greatly decreases the internal resistance and benefits the capacitance even at high current density, thus achieving high power density of the fabricated SCs. Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS) combined with nuclear magnetic resonance (NMR) spectroscopy elucidated a clear understanding of lignin chemical structure. X-ray diffraction, scanning electron microscopy, X-ray photon spectroscopy and Raman spectroscopy were applied to characterize the disordered graphitic structures in the carbon composites. A techno-economic analysis confirms the feasibility of commercializing these inexpensive lignin-based porous carbons described in this work and demonstrates competitive renewable alternatives to commercially available activated carbons.