Morphology Controlled Synthesis of Heteroatom-Doped Spherical Porous Carbon Particles Retaining High Specific Capacitance at High Current Density

Abstract

A polymer precursor based on phlorogucinol-salicyaldehyde-melamine (PSM@silica) has been synthesized using pluronic P123 and tetratethyl orthosilane as the structure directing matrix. The polymer has been pyrolyzed under nitrogen flow at different temperatures from 700 to 1000 °C to obtain the corresponding carbons, CPSM-700, CPSM-800, CPSM-900, and CPSM-1000. Carbonization temperature is found to play an important role on the morphology, heteroatom content, and surface area of the products. The samples have been characterized by various techniques such as powder X-ray diffraction, nitrogen adsorption/desorption, scanning electron microscopy and X-ray photoelectron spectroscopy studies. The spherical carbon particles of micron meter diameters with high surface area and heteroatom doping (O, N) make them potential candidates for electrochemical applications. Detailed electrochemical studies have been carried out for all the samples by cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS) in 1 M H2SO4 electrolyte. It is found that CPSM-900 shows the best results with specific capacitance of 400 F·g–1 at 0.6 A·g–1 current density. Remarkably, at high current density of 12.16 A·g–1 it still retains a very high value of 270 F·g–1. Its well-defined spherical morphology (ca. 1.16 μm diameters), high Brunauer–Emmett–Teller (BET) surface area (712 m2·g–1), and nitrogen content of ca. 2.61% are responsible for its superior performance. It shows high specific energy density and a power density of 44.92 Wh·kg–1 and 274.116 W·kg–1, respectively, at a current density of 0.6 A·g–1. The corresponding values are maintained up to 30.37 Wh·kg–1 and 5461.5 W·kg–1 at 12.16 A·g–1. The material is highly stable with no loss of specific capacitance up to 5000 cycles at 6.21 A·g–1 current density.

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