Engineering a Porous CoMn2O4/PANI Conductive Nanohybrid for High-Performance Oxygen Evolution: From Rational Architecture to Electrocatalytic Mechanism

Efficient, durable, and low-cost electrocatalysts for the Oxygen Evolution Reaction (OER) are essential for the improvement of Alkaline Water Electrolysis and sustainable hydrogen production. In this work, a conductive CoMn2O4/polyaniline (CoMn2O4/PANI) nanohybrid was successfully synthesized via a simple hydrothermal method to overcome the drawbacks of low conductivity and nanoparticle aggregation of pristine CoMn2O4. The successful incorporation of the crystalline spinel CoMn2O4 nanoparticles into the conductive PANI matrix was confirmed by structural and physicochemical characterization using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX), resulting in a porous, interconnected architecture with uniformly distributed catalytic active sites. The synergistic coupling between CoMn2O4 and PANI greatly improved electrical conductivity, active-site accessibility, electrolyte penetration, and charge-transfer kinetics. It was found that the CoMn2O4/PANI nanohybrid had a low overpotential, 373 mV at 10 mA cm−2, a small Tafel slope, 57 mV dec−1, a remarkably low charge-transfer resistance, 0.12 Ω, and a sevenfold increase in electrochemically active surface area, 350 cm2, compared with pristine CoMn2O4. In addition, the nanohybrid also proved to be extremely durable for operation, retaining the same catalytic activity after 50 h of continuous operation in alkaline OER conditions. This superior electrocatalytic activity is explained by the synergistic role of the conductive PANI network and catalytically active CoMn2O4 nanoparticles that enable fast electron transport, efficient adsorption of hydroxide ions, fast creation of oxygen-containing intermediates, and structural stability. Most significantly, this work furnishes a complete structure–property–performance relationship that delivers a fundamental understanding of how conductive polymer/spinel oxide hybridization controls the OER activity. The present results show that the hydrothermally synthesized CoMn2O4/PANI nanohybrid is an efficient electrocatalyst for oxygen evolution and present design guidelines for designing the next-generation electrocatalysts for water splitting towards sustainable hydrogen energy.