Oxygen reduction reaction and hydrogen evolution reaction catalyzed by carbon-supported molybdenum-coated palladium nanocubes

Oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) are two important processes for electrochemical energy storage and conversion. Herein, we describe the preparation of carbon-supported Pd nanocubes@Mo core@shell nanostructures as efficient dual catalysts for both ORR and HER. The core@shell structure was manifested by high resolution transmission electron microscopy measurements, including high angle angular dark field-scanning transmission electron microscopy and elemental mapping analysis. Further structural insights were obtained in X-ray diffraction and X-ray photoelectron spectroscopy measurements. The nanostructures exhibited apparent electro-catalytic activity toward both ORR and HER, and the performances were markedly higher than those without the deposition of a Mo overlayer. In ORR, the activity was even better than that of commercial Pt/C within the context of onset potential, specific and mass activities; whereas in HER, the performance of Pd nanocubes@Mo core@shell nanostructures remained subpar as compared to that of Pt/C in terms of the overpotential to reach the current density of 10 mA cm(-2), the Tafel slope was comparable and the stability was excellent. The excellent electrocatalytic performance can be attributed to the Pd-Mo synergistic effects imparted from the core-shell structure. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.