An in situ one-pot synthetic route for the synthesis of a Au@Pd/PMo12/reduced graphene oxide (rGO) nanocomposite is presented, where the Keggin-type polyoxometalate phosphomolybdic acid (PMo12) is used as both reducing and stabilizing agent. High-angle annular dark-field scanning transmission electron microscopy (HAADT-STEM), transmission electron microscopy (TEM), and X-ray diffraction analysis were applied to fully characterize the core–shell structure of Au@Pd/PMo12 on the rGO matrix. Electrochemical studies showed how this nanocomposite acts as a dual electrocatalyst for the ethanol electro-oxidation reaction (EOR) and the hydrogen evolution reaction (HER). For the EOR, the Au@Pd/ PMo12/rGO electrocatalyst offers a low onset potential of 0.77 V vs. Ag/AgCl and a high peak current density of 41 mA cm2 in alkaline medium. This feature is discussed via detailed cyclic voltammetry (CV) studies illustrating how the superior performance of the synthetic nanocomposite could be attributed to the synergistic effect of Au, Pd, PMo12 and rGO. Moreover, it has been confirmed that the proposed electrocatalyst exhibits low overpotentials for 10 mA cm2 current density (h10) in different pH media. The values of h10 were 109, 300 and 250 mV vs. RHE in acidic, basic and neutral media, respectively. Also, the ability of the electrocatalyst to provide high HER current density and its remarkable stability have been confirmed.

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