Insights on the unique electro-catalytic behavior of PtBi/C materials

Molecular dynamics simulations have been performed to study the growth and the final structure of PtxBi1-x clusters under conditions close to those encountered in classical low temperature chemical or physical synthesis methods, such as the water-in-oil route or plasma sputtering route, respectively. According to the simulations, PtxBi1-x nanoparticles should consist in well crystallized Pt core surrounded by Bi structures, with strong interaction between Pt and Bi atoms. The simulation results were compared with physicochemical characterizations of PtxBi1-x/C (x = 1.0, 0.9 and 0.8) materials synthesized at room temperature via the water-in-oil microemulsion method. XRD and XPS measurements led to the conclusion that Pt and Bi were not alloyed in PtxBi1-x nanoparticles and that the nanoparticle surface was bismuth-rich, respectively, in perfect agreement with molecular dynamics simulations. XPS and electrochemical measurements allowed also demonstrating a strong electronic interaction between Pt and Bi, still in agreement with molecular dynamics. The electrocatalytic behaviors of the PtxBi1-x/C catalysts have been studied. PtxBi1-x/C displayed the higher activity towards glycerol electrooxidation in alkaline media, with an onset potential of ca. 0.300 V vs RHE and a unique selectivity towards glyceraldehyde/dihydroxyacetone formation for potentials lower than 0.600 V vs RHE. A discussion on the relationship between composition/structure of the PtxBi1-x catalytic materials and activity/selectivity for glycerol electrooxidation allowed proposing a mechanism involving a single-carbon adsorption mode on Pt and an electronic effect for the desorption of low oxidized species from Pt sites driven by the early stage of the Bi-0 to Bi-II transition. (C) 2019 Elsevier Ltd. All rights reserved.