In this work, the catalytic activity of nanostructured core-shell electrocatalysts synthesized by the polyol and bromide anion exchange (BAE) methods was evaluated for the Hydrogen Oxidation Reactions (HOR), and the Hydrogen Evolution Reaction (HER). The electrocatalysts were supported on Vulcan (C) and nitrogen-doped graphene (NG), and labeled as Sn@Pt/C-P, Sn@Pt/NG-P, Sn@Pt/C-B and Sn@Pt/NG-B. For comparison purposes, the monometallic electrocatalysts Pt/C-P, Pt/NG-P, Pt/C-B and Pt/NG-B were synthesized. The nominal metal:support ratio in all cases was 20:80 (wt. %), while the theoretical Pt:Sn atomic relationship at the core-shell nanostructures was 1:1. EDS analysis showed a C content of approximately 80 wt. %, although in general, the experimental metals concentration was not closed to the nominal one. XRD analysis indicated the crystalline structure of the electrocatalysts, with a crystallite size of less than 7 nm. TEM characterization confirmed the formation of core-shell nanostructures, with an average particle size of ~ 2.3 nm. The highest mass activity for the HOR was shown by the Sn@Pt/C-B electrocatalyst, while in terms of specific activity its performance similar to that of Sn@Pt/C-P. On the other hand, the evaluation of the HER indicated that the best electrocatalyst considering specific activity was Sn@Pt/NG-B, which also showed the highest mass activity (like that of Sn@Pt/NG-B at low overpotentials). The results of the evaluation of catalytic activity showed that the core-shell nanostructures have an enhanced performance for the two reactions, compared with the monometallic electrocatalysts. This indicated that they are good candidates to be applied in Polymer Electrolyte Membrane Fuel Cells (PEMFC) cells, as well as in PEM electrolyzers.

Sn@Pt core-shell nanocatalysts, supported on Vulcan XC-72 and home-developed nitrogen-doped graphene (Sn@Pt/C and Sn@Pt/NG, respectively), were evaluated for the hydrogen oxidation reaction (HOR) in acid electrolyte. The nanocatalysts were synthesized by the bromide anion exchange (BAE) method. TEM characterization confirmed the nanosize nature of Sn@Pt/C and Sn@Pt/NG, with an average particle size of 2.1 and 2.3 nm, respectively. Sn@Pt/C delivered a similar mass limiting current density (jl, m) of the HOR compared to Sn@Pt/NG, which was higher than those of Pt/C and Pt/NG (ca. 2 and 2.3-fold increase, respectively). Moreover, the Sn@Pt/C and Sn@Pt/NG core-shell nanocatalysts demonstrated a higher specific activity related to Pt/C and Pt/NG. Mass and specific Tafel slopes further demonstrated the improved catalytic activity of Sn@Pt/C for the HOR, followed by Sn@Pt/NG. The application of the nanocatalysts was proposed for polymer electrolyte membrane fuel cells (PEMFC).

In this work, core-shell nanocatalysts based on Sn and Pt supported on Vulcan (Sn@Pt/C) and N-doped graphene (Sn@Pt/NG) have been synthesized by the polyol method. The core-shell nanocatalysts have been tested as anode materials for the ethylene glycol oxidation reaction (EGOR) and compared with monometallic Pt/C and Pt/NG in acid medium. Electrochemical characterization by cyclic voltammetry (CV) shows that Sn@Pt/C has a higher catalytic activity than Sn@Pt/NG, Pt/C and Pt/NG for the EGOR. For example, Sn@Pt/C generates a mass and specific current density 1.3 and 3.4 times higher than Pt/C. Sn@Pt/NG also shows higher mass and specific activity than Pt/C at low overpotentials. Moreover, Sn@Pt/C and Sn@Pt/NG oxidize COads at more negative potential than the monometallic nanocatalysts. Meanwhile, the NG support shows a positive metal-support effect, since Pt/NG is more tolerant to COads than Pt/C.