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

Abstract

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 * ISE member 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.

Binary and ternary Pt-based clusters grown in a plasma multimagnetron-based gas aggregation source: electrocatalytic evaluation towards glycerol oxidation

“…The second feature is the presence of additional peaks centered at +0.530, +0.680 and +0.880 V vs RHE for the PtBi catalyst, and at +0.580 and +0.850 V vs RHE for the PtCuBi catalyst, for the positive potential variation. In the case of PtBi/C, the shape of the CV resembles a lot that obtained on a Pt0.8Bi0.2/C catalyst prepared by a wet chemistry method (water in oil microemulsion), 8 which contradicts the EDX analysis. The oxidation peaks located at ca.…”

“…This could give us the insight that ternary PtCuBi clusters present the structure of alloyed PtCu core surrounded by a Bi shell. Molecular Dynamic simulations have already confirmed such a kind of core shell structure for the Pt-Bi system grown by GAS, having its origins in a stronger Pt-Bi bonding energy than for Pt-Pt 8 . This result agrees with other studies where Bi atoms always decorate the Pt surface and bond to two or three Pt atoms depending on the Bi content.…”

“…This result agrees with other studies where Bi atoms always decorate the Pt surface and bond to two or three Pt atoms depending on the Bi content. 8,[41][42][43] MP database 28 indicates that three stable alloys can be found for the Pt-Cu system, while two Please do not adjust margins Please do not adjust margins stable alloys are present for the Pt-Bi system. There is no data for binary alloys between Cu and Bi or ternary alloys between Pt, Cu and Bi but a metastable Cu-Bi alloy could be formed.…”

“…The oxidation peaks located at ca. +0.500 V, +0.700 V and +0.900 V vs RHE in the CV of a Pt0.8Bi0.2/C material prepared by the water in oil maicroemulsion 8 have been assigned to the oxidation reaction of bismuth according to Eq. (1).…”

Multiscale Molecular Dynamics Simulations of Fuel Cell Nanocatalyst Plasma Sputtering Growth and Deposition

“…To this end, many synthesis techniques such as plasma sputtering deposition have been investigated, including conventional magnetron, high-power impulse magnetron sputtering, and magnetron gas aggregation source depositions [4][5][6][7]. Since these deposition processes are of atomic nature, the description and insights into targeted growth processes to improve NP morphology, structure, and properties can successfully be explored using atomistic simulations, especially molecular dynamics [8][9][10][11][12][13][14][15][16]. Both growth in inert and reactive plasma environments has, thus, been shown feasible.…”