A Sustainable Approach for Preparing Porous Carbon Spheres Derived from Kraft Lignin and Sodium Hydroxide as Highly Packed Thin Film Electrode Materials

A green synthetic strategy to design biomass-derived porous carbon electrode materials with precisely tailored structure and morphology has always been a challenging goalbecause these materials can fulfill the demands of next-generation supercapacitors and other electrochemical devices. Potassiumhydroxide (KOH) is extensively utilized as an activator since itcan produce porous carbon with high specific surface area and well-developed porous channels. The exploitation of sodiumhydroxide (NaOH) as an activating agent is less referenced inthe literature, although it offers some advantages over KOH in terms of low cost, less corrosiveness, and simple handling procedure,all of which are appealing particularly from an industrial viewpoint. The motivation for this present study is to fabricate porouscarbon spheres in a sustainable manner via a spray drying approach followed by a carbonization process, using Kraft lignin as the carbon precursor and NaOH as an alternative activation agent instead of the high-cost and high-corrosive KOH for thefirst time. The structure of carbon particles can be accurately transitioned from a compact to hollow structure, and the surface textural properties can be easily tuned by altering the NaOH concentration. The obtained porous carbon spheres were applied as highlypacked thin film electrode materials for supercapacitor devices. The specific capacitance value of porous carbon spheres with a highly compact structure (high packing density) is 66.5 F g-1, which is higher than that of commercial activated carbon and other biomass-derived carbon. This work provides a green processing for producing low-cost and environment-friendly porous carbon spheres from abundant Kraft lignin and important insight for selecting NaOH as an activator to tailor the morphology and structure, which represents an economical and sustainable approach for energy storage devices.

Automated summary

This study presents a green synthesis strategy to design biomass-derived porous carbon electrode materials with precisely tailored structure and morphology using Kraft lignin as the carbon precursor and NaOH as an alternative activation agent. The obtained porous carbon spheres exhibit controlled hollow structure and tunable surface properties by adjusting the NaOH concentration. These carbon spheres show higher specific capacitance values compared to commercial activated carbon, indicating their potential for energy storage devices.