Electrocatalytic Oxidation of Methanol at a Silicon–Phosphate Modified Carbon Paste Electrode

Abstract

Direct methanol fuel cells (DMFCs) are promising electrochemical energy conversion systems; however, the sluggish kinetics of methanol oxidation and the high cost of conventional noble-metal catalysts remain significant challenges. Developing low-cost alternative electrode materials is therefore important. Silicon- and natural phosphate-modified carbon paste electrodes offer a potential approach to improving the electrochemical response towards methanol oxidation.  This study reports the fabrication and electrochemical characterisation of a carbon paste electrode modified with silicon (10 wt%) and Moroccan natural phosphate (40 wt%) for methanol electro-oxidation. A bare carbon paste electrode, composed of graphite and paraffin oil, was used as the reference. The electrodes were prepared by mixing the constituents and then packing into a cylindrical holder, providing an active surface area of approximately 0.25 cm². Electrochemical characterisation was performed in 1 M NaCl using cyclic voltammetry, square wave voltammetry, Tafel polarisation, and electrochemical impedance spectroscopy, while the electrocatalytic performance towards methanol oxidation was evaluated at different methanol concentrations. Compared with the bare electrode, the Si/NP-modified carbon paste electrode exhibited higher anodic current densities, a slightly more positive corrosion potential, and a distinct impedance response, indicating an improved electrochemical response towards methanol oxidation. The observed behaviour is consistent with the complementary roles of natural phosphate and silicon in modifying the electrode/electrolyte interface. These findings demonstrate that the Si/NP-modified carbon paste electrode is a promising low-cost candidate for methanol electro-oxidation and warrants further investigation for its potential application as an anode material in direct methanol fuel cells.