Optimal composition of paste composite electrodes based on glassy carbon matrix and iron oxides

The article considers the influence of the powder-oil ratio in the composition of paste electrodes, made of composites based on glassy carbon, on their behavior in a solution (0.1 M KCl, 0.005 M K3[Fe(CN)6], 0.005 M K4[Fe(CN)6). The obtained composite nanomaterials were studied by X-ray phase analysis, transmission and scanning electron microscopy, and X-ray spectral analysis. X-ray phase analysis showed that the sample contained graphite, magnetite Fe3O4, and cementite Fe3C. The results of scanning electron microscopy showed that particles of crystalline phases formed agglomerates ranging in size from 0.1 to 3 μm. Carbon composites were crushed and sifted through a 0.05 mm sieve, after which a paste for the electrode was prepared from the resulting powder with the ratios of the composite to vacuum oil (in mg): 80 : 5, 80 : 10, 80 : 15, 80 : 20, 80 : 25, 80 : 30. Then it was stirred into a homogeneous mass and stuffed into a tubular electrode with the 3 mm diameter. Based on a comparison of the impedance spectra and voltammograms, it has been shown that the ratio of the composite to oil that is optimal for the electrode performance is 80:10 (mass). A significant drift of the properties of freshly prepared pastes has been discovered, which is excluded by keeping them for a day before use. The decisive influence of a fresh surface before each measurement has been shown.