Sustainable production of lignin-derived porous carbons for high-voltage electrochemical capacitors

CuCl2-Activated Sustainable Microporous Carbons with Tailorable Multiscale Pores for Effective CO2 Capture

Porosity is the key factor in determining the CO2 capture capacity for porous carbon-based adsorbents, especially narrow micropores of less than 1.0 nm. Unfortunately, this desired feature is still a great challenge to tailor micropores by an effective, low-corrosion, and environmentally friendly activating agent. Herein, we reported a suitable dynamic porogen of CuCl2 to engineer microporous carbons rich in narrow micropores of <1.0 nm for solving the above problem. The porosity can be easily tuned by varying the concentration of the CuCl2 porogen. The resultant porous carbons exhibited a multiscale micropore size, high micropore volume, and suitable surface nitrogen doping content, especially high-proportioned ultromicropores of <0.7 nm. As adsorbents for capturing CO2, the obtained microporous carbons possess satisfactory CO2 uptake, moderate heat of CO2 adsorption, reasonable CO2/N2 selectivity, and easy regeneration. Our work proposes an alternative way to design porous carbon-based adsorbents for efficiently capturing CO2 from the postcombustion flue gases. More importantly, this work opens up an almost-zero cost and industrially friendly route to convert biowaste into high-added-value adsorbents for CO2 capture in an industrial practical application.

Construction of self-supporting ultra-micropores lignin-based carbon nanofibers with high areal desalination capacity

Lignin is a renewable biomacromolecule that can be used as precursors for carbon materials. In this work, highly flexible lignin-based carbon nanofibers with abundant ultra-micropores are constructed via electrospinning, oxidative stabilization and carbonization. The results indicate that replacing PAN with 80 % lignin is feasible in regulating ultra-micropores. The synthesized L4P1-CNFs possess many attractive properties (e.g., pore size distribution, electrochemical and deionization property) compared with that produced from other non-renewable precursors or more-complexed processes. It shows excellent electrochemical double-layer capacitance in 6 M KOH (233 to 162 F g^-1 at 0.5 to 5 A g^-1) and 1 M NaCl (158 to 82 F g^-1 at 0.5 to 5 A g^-1) electrolytes. Upon assembling into CDI cells, the average salt adsorption rate could reach 1.79 mg g^-1 min^-1 at 1.2 V and 3.32 mg g^-1 min^-1 at 2 V in 500 mg L^-1. Benefiting from the excellent flexibility, we innovatively stack four layers of L4P1-CNFs to improve the areal electrosorption capacity to 0.0817 mg cm^-2 at 500 mg L^-1, significantly higher than that of traditional carbon-based electrodes. The good desalination property makes lignin-based carbon nanofibers ideal for practical, low-cost capacitive deionization applications.

Recent advances in lignin-based carbon materials and their applications: A review

As the most abundant natural aromatic polymer, tens of million of tons of lignin produced in paper-making or biorefinery industry are used as fuel annually, which is a low-value utilization. Moreover, burning lignin results in large amounts of carbon dioxide and pollutants in the air. The potential of lignin is far from being fully exploited and the search for high value-added application of lignin is highly pursued. Because of the high carbon content of lignin, converting lignin into advanced carbon-based structural or functional materials is regarded as one of the most promising solutions for both environmental protection and utilization of renewable resources. Significant progresses in lignin-based carbon materials (LCMs) including porous carbon, activated carbon, carbon fiber, carbon aerogel, nanostructured carbon, etc., for various valued applications have been witnessed in recent years. Here, this review summarized the recent advances in LCMs from the perspectives of preparation, structure, and applications. In particular, this review attempts to figure out the intrinsic relationship between the structure and functionalities of LCMs from their recent applications. Hopefully, some thoughts and discussions on the structure-property relationship of LCMs can inspire researchers to stride over the present barriers in the preparation and applications of LCMs.