Nitrogen-containing mesoporous carbons with high capacitive properties derived from a gelatin biomolecule

Abstract

Nitrogen-rich mesoporous carbons were synthesized using an inexpensive and readily available gelatin biopolymer as a carbon/nitrogen precursor and colloidal silica as a hard template. The resulting materials exhibited large pore volumes of up to 4.38cm3/g, bimodal porosity (pores centered at approximately 3 and 24–28nm) and contained high levels of bulk and surface nitrogen (up to 10wt% and 5.8at.%, respectively).The electrochemical properties of the carbons were evaluated in 6M KOH and 1M H2SO4 aqueous solutions via cyclic voltammetry, galvanostatic charge/discharge cycling and electrochemical impedance spectroscopy. The samples exhibited high capacitances of up to 230 and 335F/g in alkaline and acidic solutions, respectively. The capacitance retention in the acidic solution at a high potential sweep rate (100mV/s) was lower (75–80%) than that in the alkaline medium (∼94%), suggesting that pseudocapacitance contributes less effectively in quick charge/discharge operations.The influence of the chemistry of gelatin on its compatibility with colloidal silica is discussed. It is shown that if the values of the isoelectric point of the gelatin and the pH of the colloidal silica solution are similar, then excessive self-association and precipitation may occur, thereby decreasing the porosity of the resulting carbons.