Electrocatalyst for ethanol oxidation reaction based on isatin-modified chitosan

Direct Ethanol Fuel Cells have garnered significant attention in recent years due to their potential for producing clean and renewable energy. These systems were particularly appealing for their low toxicity and high current density. This study investigated the catalytic activity of an isatin-modified chitosan Schiff base in ethanol electrooxidation for possible Direct Ethanol Fuel Cells applications. Density functional theory calculations and experimental analysis were employed to assess the relative stability of two protonated models between two protonated models of an isatin-modified chitosan Schiff base using Gibbs free energy, where the proposition of the most stable model in enthalpy and entropy (ΔH = − 15.37 kcal mol⁻¹ and TΔS = 1.16 kcal mol⁻¹) is in agreement with the spectroscopy data in the ultraviolet and visible region. The synthesized isatin-modified chitosan Schiff base was structurally characterized through nuclear magnetic resonance spectroscopy, Fourier-transform infrared spectroscopy, Ultraviolet–Visible spectroscopy, and thermogravimetric analysis. Scanning electron microscopy provided morphological insights into formation and structure. In electrocatalytic experiments, a carbon paste electrode with 5% isatin-modified chitosan efficiently oxidized ethanol, especially at pH 3, where protonation of hydroxyl and amino groups in chitosan favored the process. Current density increased proportionally to ethanol concentration and electrochemical impedance spectroscopy showed the sensor's capacitive behavior, indicated by high double layer capacitance. Results suggested that the isatin-modified chitosan Schiff base holds promise as a potential electrocatalyst for ethanol oxidation, offering a more sustainable and efficient alternative to platinum-based catalysts.