Polyaniline-supported Ag₂O/Mn₂O₃ nanostructures on nickel foam for efficient bifunctional water splitting electrocatalysis

In this study, a series of Ag₂O/Mn₂O₃ hybrid nanomaterials was successfully synthesized via a facile co-precipitation route followed by calcination at different temperatures of 550 °C, 650 °C, 700 °C, and 750 °C, designated as AM-1 to AM-4, respectively. The influence of calcination temperature on the structural, morphological, and electrochemical properties of the composites was investigated. Among these, AM-1, calcined at 550 °C, exhibited the most favorable characteristics, including uniform particle distribution with reduced agglomeration, suitable crystallinity, and enhanced electrocatalytic water splitting activity. To further improve the catalytic performance, AM-1 was incorporated into a conductive polyaniline (PANI) substrate at different weight ratios of AM-1 to PANI (1 : 1, 2 : 1, 3 : 1, and 5 : 1) to form hybrid catalysts denoted as AM-1@PANI(x : 1). The synergistic interaction between the metal oxide and polymer phases significantly improved charge transfer efficiency and increased the accessibility of active sites. Among all composites, AM-1@PANI(5 : 1) loaded onto nickel foam (NF) exhibited the best electrocatalytic performance for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), with low overpotentials of 309 mV and 139 mV at 10 mA cm⁻² and Tafel slopes of 69.8 and 125.3 mV dec⁻¹, respectively. Additionally, this nanocomposite achieved an overall water-splitting cell voltage of 1.62 V at 10 mA cm⁻² in a self-supported two-electrode system, maintaining excellent stability for at least 24 hours. These results demonstrate that Ag₂O/Mn₂O₃@PANI hybrid systems are promising, low-cost, and efficient bifunctional catalysts for sustainable water-splitting applications.