Dual-Functional PdAg Alloy Oxygen Electrocatalyst for Stable Operation in Zinc–Air Batteries and Proton Exchange Membrane Fuel Cells

High overpotential resulting from the slow reaction rate of the oxygen reduction reaction (ORR) at air electrodes limits the practical use of proton exchange membrane fuel cells (PEMFCs) and zinc–air batteries (ZABs). In this study, a simplified single-step synthesis of PdAg alloy nanoparticles loaded on reduced graphene oxide (PdAg-rGO) as a bifunctional catalyst for the ORR and the oxygen evolution reaction (OER) was designed. Electrochemical evaluations revealed that the PdAg-rGO electrocatalyst showed a good ORR E_onset potential in alkaline (0.87 V) and acidic media (0.74 V). For the OER, PdAg-rGO required a 290 mV overpotential to deliver 50 mA cm^–2 and a Tafel slope of 61 mV dec^–1. Notably, PdAg-rGO demonstrated long durability, maintaining stable performance over 120 h in ZAB and over 100 h in PEMFC tests. The findings highlight the practical potential of the PdAg alloy as a robust and versatile ORR catalyst for emerging technologies in energy systems.