Highly Efficient Bifunctional Catalyst of Pd/PdO x on 1D α-MnO2 Nanorods for Overall Water Splitting Reaction in Alkaline Medium

Abstract For overall water-splitting reactions, advancements in the synthesis of efficient and durable bifunctional catalysts are essential. Within this study, Pd/PdOx on 1D α-MnO2 nanorods was synthesized to utilize strong metal-oxide interactions and develop a bifunctional catalyst for water electrolysis. Morphological and surface analyses confirmed the formation of 1D α-MnO2 nanorods with a distribution of localized Pd/PdOx active sites, which lowers recombination resistance compared to α-MnO2. The optimized α-MnO2/Pd/PdOx electrode exhibited promising activity in the electrocatalytic hydrogen evolution reaction (HER) at −10 mA cm–2 with an overpotential of 0.170 V vs RHE, with a Tafel slope value of 93 mV/dec; on the other hand, in the case of the oxygen evolution reaction (OER), the catalyst at 10 mA cm–2 showed an overpotential of 330 mV vs RHE with a Tafel slope value of 70 mV/dec in alkaline medium. The overpotential required for overall water-splitting reaction is 1.73 V to achieve a benchmark current density in both half-cycles. The improved bifunctional performance is attributed to the synergistic interaction between Mn3+ and defect oxygen species in 1D α-MnO2 nanorods with localized Pd/PdOx nanoparticles, which facilitates rapid interfacial charge transfer, modulates the local environment, and promotes defect-associated oxygen/hydroxyl species, thereby enhancing the catalytic activity. This observation infers that, for overall water-splitting reaction in alkaline medium, α-MnO2/Pd/PdOx is a promising electrocatalyst and can be further developed for electrolyzer applications.