KOH activation of carbon-based materials for energy storage

Abstract

Because of their availability, adjustable microstructure, varieties of forms, and large specific surface area, porous carbon materials are of increasing interest for use in hydrogen storage adsorbents and electrode materials in supercapacitors and lithium-sulfur cells from the viewpoint of social sustainability and environmental friendliness. Therefore, much effort has been made to synthesize and tailor the microstructures of porous carbon materials via various activation procedures (physical and chemical activation). In particular, the chemical activation of various carbon sources using KOH as the activating reagent is very promising because of its lower activation temperature and higher yields, and well-defined micropore size distribution and ultrahigh specific surface area up to 3000 m 2 g À1 of the resulting porous carbons. In this feature article, we will cover recent research progress since 2007 on the synthesis of KOH-activated carbons for hydrogen and electrical energy storage (supercapacitors and lithium-sulfur batteries). The textural properties and surface chemistry of KOH-activated carbons depend on not only the synthesis parameters, but also different carbon sources employed including fossil/biomass-derived materials, synthetic organic polymers, and various nanostructured carbons (e.g. carbon nanotubes, carbon nanofibers, carbon aerogels, carbide-derived carbons, graphene, etc.). Following the introduction to KOH activation mechanisms and processing technologies, the characteristics and performance of KOH-activated carbons as well as their relationships are summarized and discussed through the extensive analysis of the literature based on different energy storage systems. Jiacheng WangJiacheng Wang received his PhD in materials physics and chemistry from Shanghai Institute of Ceramics, Chinese Academy of Sciences in 2007 under the supervision of Prof. Qian Liu. After three and a half years of postdoctoral research as a project researcher and then a JSPS postdoctoral fellow at the University of Tokyo, he joined the research group of

Designing micro- and mesoporous carbon networks by chemical activation of organic resins

“…However, the activation of xerogels typically provokes the loss of the meso/macroporosity. These results contrast with herein reported data, as the mesoporosity of the precursor is inherited by the samples activated using K 2 CO 3 , but not in the case of KOH (these alkaline hydroxides are commonly used in the literature), which may be linked to the fact that KOH is more effective than K 2 CO 3 for activation (Wang and Kaskel 2012;Mestre et al 2014Mestre et al , 2015. To further understand this behavior, we have explored the effect of the impregnation procedure (physical mixing and wet impregnation) for both activating agents, aiming to design a simple approach for the synthesis of highly nanoporous carbon gels with bimodal micro/mesoporous structure.…”

“…Porous carbon materials normally have relatively broad pore-size distributions in both micropore and mesopore ranges, being the porosity dominated by the micropore structure (Marsh and Rodriguez-Reinsono 2006;Wang and Kaskel 2012).…”

High rate performance activated carbons prepared from ginkgo shells for electrochemical supercapacitors

“…The specific capacitance of GAC is 365 F g À1 at 2 mV s À1 , which is quite higher than that of the commercial activation carbons. But GAC exhibits a poor rate performance as most of the activated carbons reported in the literature [31]. The specific capacitance of GAC is also higher than that of GGAC at low scan rate.…”

Synthesis of 3D porous carbon based on cheap polymers and graphene foam for high-performance electrochemical capacitors

“…The activation of the preformed PVA/GF/PVP hydrogel by KOH further enhances the porosity of the hydrogel structure by the efficient intercalation of potassium ions in the carbon lattice of the polymer network. The role of KOH in the activation of carbon materials has been summarized as the result of a series of synergistic reactions, which include chemical activation, physical activation and carbon lattice expansion by the metallic K intercalation [23]. The resulting activated carbon obtained from the PVA/GF/PVP hydrogel after the carbonation process through annealing thus guaranteed a highly dense porosity which should be coupled with a highly improved conductive surface area.…”