Research Article Cite This: ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
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Scalable Synthesis of Uniform Nanosized Microporous Carbon Particles from Rigid Polymers for Rapid Ion and Molecule Adsorption Fei Ji,† Yang Shi,† Mingqian Li,† Shengli Jiang,† Gen Chen,‡ Fang Liu,† and Zheng Chen*,† †
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Department of Nanoengineering, University of California, San Diego 9500 Gilman Drive, La Jolla, San Diego, California 92093, United States ‡ Department of Chemical and Biomolecular Engineering, University of California, Los Angeles, 420 Westwood Plaza, Los Angeles, California 90095, United States S Supporting Information *
ABSTRACT: Porous carbon materials are of great importance for many applications such as energy storage, catalysis, and adsorption. Rational design and low-cost synthesis of carbon structures that can simultaneously offer high surface area and rapid ion/molecule transport properties remain desired for target functions. Here, we report a cost-effective and scalable synthesis of high surface area, size-uniform microporous carbon nanoparticles. A combination of using rigid polymer nanoparticles as the precursor, precarbonization, and activation process leads to carbon nanoparticles with a high surface area (up to 2789 m2 g−1), a large pore volume (up to 1.85 cm3 g−1), and a high packing density (0.5 g cm−3), which is due to the existence of a large amount of highly accessible micropores. Such a unique carbon structure exhibits not only large capacity but also rapid adsorption for both ions and small molecules, demonstrated in high-performance supercapacitors and as an efficient sorbent for removal of pollutants from water. This study provides a new strategy that can be used to further design and tune nanostructured carbon and composite particles to explore many other applications. KEYWORDS: porous carbon, nanoparticles, energy storage, supercapacitors, adsorption
1. INTRODUCTION Porous carbons with high surface area have attracted extensive attention during the past decades. Their high electronic conductivity, good chemical stability, and high adsorption capability are of great interest for wide applications such as supercapacitors,1−5 metal−air batteries,6−8 electrocatalysis,9−12 and water treatment.13−16 Traditional microporous activated carbons (ACs) are predominantly used for commercial applications because of their well-established manufacturing process, relatively low cost, and easy production in large scale. The common strategy to produce ACs is based on chemical activation. Strong acid or base is often used to activate the carbon precursors such as coal or biomass (e.g., coconut shell, rice husk, and bamboo).14,17,18 However, these porous carbons normally contain a large amount of impurities, which require extra steps for purification.19 Moreover, such carbons are usually in the form of bulk particles (e.g., micron-size) and have tortuous pore structures, which render limited mass transport kinetics for absorption. For example, in supercapacitor electrodes, ACs can provide reasonably high capacitance because of the large amount of micropores, but their rate capability is generally moderate because of retarded electrolyte ion migration, which prevents them from highpower applications.20 To overcome this problem, it is crucial to reduce the effective diffusion length. One strategy is to design hierarchi© XXXX American Chemical Society
cally porous structures, which combines macropores, mesopores, and micropores.1,21,22 In such a structure, macropores serve as the electrolyte reservoirs, whereas mesopores act as local channels for fast mass transport and micropores contribute to the high ion or molecule adsorption capacity, which overall ensures the short diffusion paths and fast mass transport even in the relatively large carbon particles. However, hierarchically porous carbons are generally synthesized by using templates. Hard templates (such as SiO2 and NaCl)23,24 or soft templates (such as polymers and surfactants)25 are mixed with carbon precursors for carbonization and then removed to create pores, which increases the overall cost and makes them difficult for large-scale production. An alternative strategy is to fabricate various low-dimensional nanosized porous carbons. Two-dimensional and onedimensional structures, such as graphene and carbon nanotubes (CNTs), have been designed to produce various porous structures, which show excellent rate performance.26−29 However, these carbon materials often suffer from low density (
