Synergistic NiO–Mn2O3 Composite Thin Films via Facile Dip-Coating: A Cost-Effective and Stable Electrocatalyst for Methanol Oxidation in Alkaline Direct Methanol Fuel Cells

Abstract

The commercialization of direct methanol fuel cells (DMFCs) is hindered by the high cost, limited durability, and sluggish kinetics of platinum-based catalysts. To address these challenges, NiO/FTO, Mn₂O₃/FTO, and NiO–Mn₂O₃/FTO thin films were fabricated using a simple and low-cost dip-coating method. Structural and compositional analyses using SEM and EDS confirmed the formation of uniform and porous morphologies, while XRD and Raman spectroscopy verified the crystalline nature and phase formation of the materials. Among the prepared electrodes, the NiO– Mn₂O₃/FTO composite exhibited superior electrocatalytic activity for methanol oxidation, delivering a prominent anodic peak at 0.99 V and a maximum current density of 5.8 mA cm⁻². At 0.65 V, it achieved a current density of 2.5 mA cm⁻² in 1.4 M methanol at a scan rate of 100 mV s⁻¹. Chronoamperometric measurements demonstrated good electrochemical stability, with 86% current retention after 2000 s. Electrochemical impedance spectroscopy further confirmed the enhanced charge-transfer capability, showing a significantly lower charge-transfer resistance (R_ct) of 71 Ω compared with 349 Ω for NiO and 517 Ω for Mn₂O₃ electrodes. Overall, the NiO–Mn₂O₃/FTO thin film offers a cost-effective, stable, and efficient catalytic system, demonstrating strong potential as an alternative anode material for DMFC applications.