Nanocomposite Mn ₃ O ₄ -RuO ₂ Oxygen Evolution Reaction Catalysts for Proton Exchange Membrane Water Electrolysis

Hydrogen production via proton exchange membrane water electrolysis (PEMWE) is constrained by the sluggish kinetics of the oxygen evolution reaction (OER) at the anode, which typically requires catalysts rich in noble metals such as iridium (Ir) and ruthenium (Ru) in acidic media, leading to high costs. In this work, Mn3O4-RuO2 nanocomposites were synthesized via a hydrothermal reaction. The morphology, structure, and chemical composition of the catalysts were characterized by XRD, SEM, TEM, EDS, and XPS. The results indicate that the Mn3O4 spinel structure was successfully incorporated into the rutile structure of RuO2, forming a nanocomposite. XPS analysis revealed that the introduction of Mn results in an increased electron density on Ru species, yielding a Mn3O4-RuO2 catalyst with low Ru loading and Ru4+ species in an electron-enriched state. The OER activity parameters, including overpotential at 10 mA·cm−2, mass activity, and Tafel slope, were evaluated using the three-electrode system. The 20% Mn3O4-RuO2 composite exhibited superior activity and good stability under acidic conditions: an OER overpotential (η10) of 200 mV at 10 mA·cm−2, a mass activity of 231 A·g−1 Ru, and a Tafel slope of 53.97 mV·dec−1, outperforming the pure RuO2 catalyst. Durability was assessed via chronoamperometry (CA) and chronopotentiometry (CP), which showed that the performance decay rate of the 20% Mn3O4-RuO2 sample was lower than that of pure RuO2. This study provides a strategy for designing low-cost, acid-stable OER electrocatalysts for energy conversion applications.