Synthesis and capacitance performance of phosphorous-enriched carbon xerogel

Abstract

Phosphorous-enriched nanoporous carbon materials gained much interest as electrodes used in the electrical double layer capacitors due to their large and prolonged electrochemical energy storage. In this work, two carbon xerogels (CX and CX-P) prepared from resorcinol–formaldehyde before and after chemical treatment with phosphoric acid were studied as electrode materials. Phosphoric acid treatment efficiently produced the phosphorous functional groups in the framework of carbon xerogel, enhancing the electrochemical capacitance. Samples were characterized by means of field emission scanning electron microscopy, nitrogen adsorption at −196 °C, fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The electrochemical behaviors were demonstrated by cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy. Although low significant changes in the morphology and porosity were made on CX-P xerogel, a remarkable abundant in the phosphorous-containing oxygen functional groups was developed with the chemical treatment. Efficiently produced phosphorous functional groups in the carbon xerogel framework enhanced the electrochemical capacitance to large extent. Capacitance value was increased 4.8 times from 38 F/g for CX electrode to 183 F/g for CX-P electrode at 5 mV/s. Moreover, CX-P preserved about 79% of capacitance on 200 mV/s scan rate. CX-P electrode exhibited identical triangular type charge-discharge curves throughout the increases in the current densities from 1 to 20 A/g, very promising for electrochemical capacitor applications.