Abstract
Porous carbon spheres (CSs) have distinct advantages in energy storage and conversion applications. We report the preparation of highly monodisperse N-doped microporous CSs through the carbonization of polystyrene-based polymer spheres and subsequent activation. The N-doped microporous CSs have a remarkably high N-doping content, over 10%, and high BET surface area of 884.9 m2 g−1. We characterize the synergistic effects of the micropores and N doping on the energy storage performance of a supercapacitor electrode consisting of the CSs and on the performance in an electrocatalytic reaction of a CS counter electrode in a photovoltaic cell. The N-doped microporous CSs exhibit a maximum capacitance of 373 F g−1 at a current density of 0.2 Ag−1, a high capacitance retention up to 62% with a 10-fold increase in current density, and excellent stability over 10,000 charge/discharge cycles. A counter electrode consisting of N-doped microporous CSs was found to exhibit superior electrocatalytic behavior to an electrode consisting of conventional Pt nanoparticles. These CSs derived from polymer spheres synthesized by addition polymerization will be new platform materials with high electrochemical performance.
Highlights
Carbon nanomaterials is used in electrodes for energy storage and conversion applications such as supercapacitors, lithium-ion batteries, catalytic supports in fuel cells, and photocatalytic and electrocatalytic conversion[1,2,3]
The XRD results obtained at various temperatures up to 700 °C indicate that K2CO3 is produced at 600 °C, and at 700 °C K2O is produced while K2CO3 is reduced
The preparation of microporous, heteroatom-doped carbon spheres (CSs) is a synergistic strategy for improving their energy storage/conversion efficiency
Summary
Carbon nanomaterials is used in electrodes for energy storage and conversion applications such as supercapacitors, lithium-ion batteries, catalytic supports in fuel cells, and photocatalytic and electrocatalytic conversion[1,2,3]. Polypyrrole, polysaccharide carrageenan, and polybenzoxazinespheres have been utilized as CS precursors[14,15] Such polymer-derived CSs are typically non-porous and dense. N doping enhances electrocatalytic properties: it improves the chemisorption of oxygen, which results in high performances in electrocatalytic oxygen-reduction reactions[14]. Despite these advantages of N doping, there have been few attempts to prepare N-doped CSs. N-enriched porous CSs have been prepared by carbonizing phenolic resin polymer spheres, and were used in a supercapacitor[31,32]. The CSs derived from PS-based materials provide a new platform for high performance electrochemical nanomaterials
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