Featured Contributes of Pd–Co-Decorated MnO2 NPs toward ORR Kinetics in Low-Temperature Fuel Cells: Outstanding Electrocatalysis Eliminating Pt and Carbon from Electrodes

Abstract

The present study explores the contributory benefits of transition metals (TM) and their oxides (TMO) along with metal NPs toward oxygen reduction reaction (ORR) in alkaline medium for low-temperature direct ethanol fuel cells (DEFCs). The metal–co-metal (Pd–Co) NPs were casted over a TMO support, α-MnO2, by a green synthetic approach without using any reducing agent, whereby the introduction of >30% Co in the Pd matrix formulates the optimal catalyst composition Pd69Co31/MnO2 that not only reduces the cost and eliminates the carbon support but also ensures the catalytic efficacy for the binary system. The studies involved morphology determined through electron microscopy and electrochemical characterization with the help of potentiodynamic polarization and rotating disk electrode─rotating ring–disk electrode techniques. The diminution of ORR overvoltage by ∼85 mV with respect to Pd/C establishes the catalytic pre-eminence of the nanostructured Pd69Co31/MnO2 manifested by the low yield of H2O2 in ORR and an appreciable power density output of 45.5 mW/cm2 for a single test cell at 40 °C. The autocatalytic peroxide removal capacity of the MnO2 support and synergistic interaction within Pd–Co NPs for driving the ORR catalytic ability to a substantial level are the testaments to the major utility of the combinatorial (metal–TM–TMO) ensemble.