High-yield production of porous carbon spheres derived from enzymatic hydrolysis lignin for zinc ion hybrid capacitors

The widespread implementation of supercapacitors is hindered by the limited energy density and the pricey porous carbon electrode materials. The cost of porous carbon is a significant factor in the overall cost of supercapacitors, therefore a high carbon yield could effectively mitigate the production cost of porous carbon. This study proposes a method to produce porous carbon spheres through a spray drying technique combined with a carbonization process, utilizing renewable enzymatic hydrolysis lignin as the carbon source and KOH as the activation agent. The purpose of this study is to examine the relationship between the quantity of activation agent and the development of morphology, pore structure, and specific surface area of the obtained porous carbon materials. We demonstrate that this approach significantly enhances the carbon yield of porous carbon, achieving a yield of 22% in contrast to the conventional carbonization-activation method (9%). The samples acquired through this method were found to contain a substantial amount of mesopores, with an average pore size of 1.59 to 1.85 nm and a mesopore ratio of 25.6%. Additionally, these samples showed high specific surface areas, ranging from 1051 to 1831 m 2 ·g −1 . Zinc ion hybrid capacitors with lignin-derived porous carbon cathode exhibited a high capacitance of 279 F·g −1 at 0.1 A·g −1 and an energy density of 99.1 Wh·kg −1 when the power density was 80 kW·kg −1 . This research presents a novel approach for producing porous carbons with high yield through the utilization of a spray drying approach.