Evidence of the Strong Metal Support Interaction in a Palladium-Ceria Hybrid Electrocatalyst for Enhancement of the Hydrogen Evolution Reaction

Abstract

A facile two-step method was developed to synthesize a novel Pd/CeO2/C hybrid electrocatalyst for the hydrogen evolution reaction (HER) in alkaline media. Compared to Pd/C, CeO2/C, and a physical mixture of Pd/C and CeO2/C, the Pd/CeO2C hybrid exhibited a superior HER electrocatalytic activity. Stable performance of the Pd/CeO2/C hybrid was achieved during a 12 h chronopotentiometry test at 15 mA cm−2. The improved HER activity and stability can be attributed to the presence of CeO2 not only as a support for anchoring and stabilizing of Pd nanoparticles, but also via strong interaction between Pd and CeO2. Here an intimate contact between Pd and CeO2 nanoparticles and the strong metal support interaction were demonstrated by high resolution transmission electron microscopy (HR-TEM) and X-ray absorption spectroscopy (XAS). The electron transfer from Pd to CeO2 that results in Pd in the oxidized form was also shown by X-ray photoelectron spectroscopy (XPS). The XAS measurements additionally demonstrated that the surface Pd was partially oxidized to Pd oxide, and the formation of a plausible Pd-O-Ce structure in the Pd/CeO2/C hybrid.