Unraveling porogenesis in nitrogen rich K+-activated carbons

Abstract

Though potassium activation is one of the most common methods for producing high surface area porous carbons, a detailed understanding of the influence of precursor properties on the resulting physicochemical properties is lacking. To this end, polycondensation products of sucrose and melamine served as a useful platform to understand the role of precursor N content on the surface chemistry and porosity after potassium activation. By manipulating the nitrogen:carbon:potassium ratios in the precursors, a suite of porous carbons with variable surface areas (528–2740 m2/g) and nitrogen contents (0–22 at%) were synthesized. Analysis of both the byproducts and the carbons’ resulting physicochemical properties revealed a complex interplay of various known reaction schemes (viz., gas evolution, carbothermal reduction, chemical etching, and molten salt templating), which are not mutually exclusive and can each contribute to the resulting porosity and surface chemistry. With this comprehensive study and careful control of the precursor composition, we define specific nitrogen:potassium regimes where certain porogenesis pathways dominate. Our work emphasizes that straightforward mechanisms focused on carbothermal reduction and exfoliation cannot always explain porogenesis in nitrogen-rich carbons. This work endeavors to serve as a roadmap for greater understanding and control of the structure and chemistry of nitrogen-rich, potassium-activated porous carbons.