Sustainable lignin-derived hierarchically porous carbon for capacitive deionization applications

Abstract

In this work, hierarchical porous carbons were fabricated via an environmentally friendly and sustainable approach involving self-assembly of a cross-linked lignin polymer with a less toxic cross-linker and a triblock copolymer template. The porous carbons obtained by using different cross-linking agents were evaluated by N₂ adsorption/desorption analyses, scanning electron microscopy, and transmission electron microscopy, revealing a tunable ratio of mesopore to micropore volume. The utilization of lignin-derived porous carbons for capacitive deionization (CDI) was investigated. The results showed that a porous carbon electrode with a higher mesoporosity (a lower specific surface area) exhibited higher salt adsorption capacity and a better rate capability, compared to the high specific surface area of a micro-dominant porous carbon electrode. The contribution of mesopores was to promote the ion transfer into the interior pores, providing a more accessible surface area, thus improving the capacity of ion storage. This work presents an example of CDI utilization and a value-added approach of bio-based lignin materials as promising electrode materials for desalination applications.