Preparation of Glassy Carbon Microspheres for Use in Electrochemical Analysis

Abstract

A new method for producing glassy carbon microspheres in solutions containing furfuryl alcohol, ethylene glycol, isooctylphenol decaglycol ether (OP-10), and sulfuric acid was developed. The morphology of the microspheres was examined. Their electrochemical tests in a solution containing 0.1 M KCl, 0.005 M K₃[Fe(CN)₆], and 0.005 M K₄[Fe(CN)₆] were performed. The relationship between the solution temperature during the synthesis (the heat released in the polycondensation reaction) and the volume of the acid added was established using a noncontact thermometer. The polymer microspheres obtained in the solution were washed, dried, and calcined at 900°C. The materials obtained were examined by scanning electron microscopy and X-ray fluorescence elemental analysis. The elemental analysis showed that the materials contained about 98% carbon and less than 2% potassium, copper, oxygen, sulfur, and iron. Scanning electron microscopy revealed that the microspheres had a regular spherical shape, a developed surface, and the diameter ranging from 0.5 to 10 μm. The characteristic microsphere size was determined by dynamic light scattering, and the dependences of the size on the reactant ratio during the synthesis were constructed. A paste with the microsphere to vacuum oil weight ratio of 80 : 10 was prepared for the electrode fabrication. This mixture was stirred to obtain a homogeneous paste and stuffed into a tubular electrode 3 mm in diameter. The peak current and peak potential values determined using cyclic voltammetry for the electrodes with pure microspheres and, for the best sample, with the addition of barium hexaferrite as an electrochemical catalyst. Among the nineteen solutions studied, the solution containing 100 mL of ethylene glycol, 5 mL of furfuryl alcohol, 5 mL of OP-10, and 50 mL of sulfuric acid is the most promising.