Nanocomposite with Promoted Electrocatalytic Behavior Based on Bimetallic Pd-Ni Nanoparticles, Manganese Dioxide, and Reduced Graphene Oxide for Efficient Electrooxidation of Ethanol

In this work, a nanocomposite containing manganese dioxide (MnO2) modified reduced graphene oxide (rGO) supported bimetallic palladium nickel (Pd-Ni) catalyst is prepared by electrodeposition method. The nanocomposite modifier film is prepared by forming a thin layer of graphene oxide (GO) via drop-casting of GO nanosheet dispersion on glassy carbon electrode (GCE), followed by electrochemical reduction of the film to provide rGO/GCE. Then, a two-step potential procedure is applied to deposit MnO2 nanoparticles on rGO/GCE. At the optimum deposition conditions, MnO2 nanoparticles with a thickness of 30-50 nm homogeneously covered the rGO surface (MnO2/rGO/GCE). Finally, the bimetallic Pd-Ni nanoparticles are electrodeposited on MnO2/rGO/GCE at a fixed potential to form a uniform dispersion with an average particle size of about 50 nm (Pd-Ni MnO2/rGO/GCE). The morphology and crystalline structure of the prepared nanocomposites are characterized using XRD, SEM, EDX, FTIR, AFM, and Raman spectroscopy. The catalytic activities of different electrodes based on Pd/GCE, Pd/C/GCE, Pd/rGO/GCE, Pd-Ni/rGO/GCE, and Pd-Ni/MnO2/rGO/GCE for ethanol oxidation are compared using cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy (EIS). The results revealed significantly higher electroactive surface area (ECSA), higher catalytic activity, and better stability of Pd-Ni MnO2/rGO/GCE toward the electrooxidation of ethanol compared to the other electrodes. The overall results corroborate the role of MnO2, Ni, and rGO as important constituents that significantly improve the electrocatalytic behavior, stability, and CO poisoning tolerance of Pd during the electrooxidation process. Thus, the prepared Pd-Ni MnO2/rGO/GCE catalyst can be considered as a promising anode catalyst for alkaline direct ethanol fuel cells.