Highly N-doped microporous carbon nanospheres with high energy storage and conversion efficiency

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.