Composites Electrodes Based on Castor Oil Derivatives and Graphite: Synthesis, Properties and Electroanalytical...

In this study, solid composite electrodes based on an epoxidized and maleinized castor oil polymer (ECO-MECO) and graphite were prepared and characterized to evaluate their thermal, morphological, and electrochemical properties. Composites were formulated with varying graphite contents (50-85 wt %). Thermogravimetric analysis (TGA) confirmed the homogeneity of the composites as well as their graphite contents, revealing two main mass loss events corresponding to the decomposition of the agglutinant and the subsequent oxidation of graphite. Scanning Electron Microscopy (SEM) images showed a progressive increase in the amount and distribution of graphite lamella with higher graphite content, indicating improved dispersion and interfacial interaction. Contact angle measurements demonstrated that the addition of graphite reduced surface hydrophobicity, enhancing wettability. Electrochemical performance was investigated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), with results compared to a glassy carbon electrode (GCE). Composites containing 70% and 80% graphite (wt %) exhibited comparable or superior peak currents relative to GCE. The 70% graphite (wt %) composite was selected for preparation of electrodes and surface activation studies. After electrochemical treatment in phosphate solutions at different pH values, the electrode showed enhanced redox responses under both anodic and cathodic probes compared to GCE. Bode-phase analysis revealed a shift toward lower frequencies, indicating increased capacitive behavior. This transition was attributed to the formation of oxygenated functional groups on the electrode surface, which enhance charge storage and interfacial reactivity. Differential pulse voltammograms of Pb²⁺ and dopamine revealed that the analytical signal can be enhanced by preconcentration step and surface treatment, respectively. These results highlight the potential of biopolymer-graphite composites as sustainable materials for electrochemical sensing applications.