Compared to the acidic hydrogen evolution reaction (HER), the sluggish reaction rate in an alkaline electrolyte makes it a priority to develop highly efficient and cost-effective catalysts. Incorporation of Pt with transition metals to form alloy nanocrystals with different structures and atomic distributions has been reported as a promising approach to enhance HER activity and improve Pt utilization. However, whether the structural ordering of the Pt-based bimetallic alloy affects the HER activity still remains unknown. Here, we synthesized PtNi/C nanoparticles through a modified coprecipitation method and obtained their ordered and disordered phases at different annealing temperatures in a reducing atmosphere. It is contrary to our expectation that the disordered PtNi/C exhibited a superior activity toward the HER in alkaline media compared with the ordered PtNi/C. To understand this interesting phenomenon, a systematic study combining X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy (XAS) was conducted. In addition, we studied the mechanism of the HER in an alkaline electrolyte based on newly constructed models. The density functional theory (DFT) calculation demonstrated that the unexpected activity change may be attributed to the synergistic effect between the formation of Ni/Pt–OH bonds and the increased degree of disorder of Pt and Ni atoms on their surface.

A facile two-step method was developed to synthesize a novel Pd/CeO 2 /C hybrid electrocatalyst for the hydrogen evolution reaction (HER) in alkaline media. Compared to Pd/C, CeO 2 /C, and a physical mixture of Pd/C and CeO 2 /C, the Pd/CeO 2 C hybrid exhibited a superior HER electrocatalytic activity. Stable performance of the Pd/CeO 2 /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 CeO 2 not only as a support for anchoring and stabilizing of Pd nanoparticles, but also via strong interaction between Pd and CeO 2 . Here an intimate contact between Pd and CeO 2 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 CeO 2 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/CeO 2 /C hybrid.

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