Pair Distribution Function Analysis and Electrochemical Performance of Mesoporous Carbon Nanomaterials Synthesized Through KOH and ZnCl2 Activation

Abstract

Mesoporous carbon has been synthesized by activating carbonized biogas slurry residues with ZnCl₂ and KOH simultaneously. The carbon to activating agent mass ratios were kept at 1:4, while the ZnCl₂ to KOH mass ratio varied from 4:0, 3:1, 2:2, 1:3, to 0:4. The highest BET specific surface area of 361 m² g^-1, micropore surface area of 231 m² g^‒1, mesopore surface area of 125 m² g^‒1, and total pore volume of 0.23 cm³ g^‒1 which amounted to 78% mesopore content, were obtained for the sample with 3:1 ZnCl₂ to KOH mass ratio. Scanning electron microscope (SEM) images were acquired to determine the surface morphology and energy dispersive X-ray (EDX) was used to determine surface composition of the samples. The short, medium, and long-range orders of the synthesized materials were studied using pair distribution function (PDF) analysis. PDF showed that in addition to the locally ordered carbon and silica phase components, samples activated using combined ZnCl₂ and KOH also contained crystalline Zn₂SiO₄ phase with the willemite structure. Electrochemical studies in three-electrode cell system revealed maximum specific capacitance of 216 F g^‒1 exhibited by sample with a ZnCl₂: KOH mass ratio of 3:1 at a scan rate of 5 mV s^‒1.

Keywords: Mesoporous carbon; Pair distribution function, Specific capacitance, supercapacitor