This project aims at synthesizing highly active and durable “hollow” Pt nanocrystallites that may be capable of fulfilling cost, performance, and durability requirements of proton-exchange membrane fuel cell applications (PEMFC). M/C nanoparticles ( M = Co, Ni, Cu) will first be synthesized, then a galvanic displacement will allow adorning the M surface by controlled number of Pt monolayers, yielding ultimately “hollow” Pt nanocrystallites (core supported Pt monolayer electrocatalysts). If only a monolayer of Pt is deposited, 100 % of the Pt atoms are used in the electrochemical reaction, which allows saving costly Pt atoms. In order to control the synthesis process and to bridge the electronic structure of the hollow Pt nanocrystallites and their electrocatalytic activity/durability properties, the nanoparticles will be thoroughly characterized from the initial stage (core/shell nanoparticles) up to the “hollow” Pt nanoparticles, passing through different atomic rearrangement steps. At this scale and in the case of multi-elemental particles, advanced transmission electron microscopy techniques will be required.

Fig 1: Schematic view of the synthesis route for hollow Pt nanocrystals.

The factors that will possibly influence the electrocatalytic activity of the “hollow” Pt/C nanocrystallites are the nature of the sacrificial M metal and the Pt:M stoichiometry in the deposition solution. Such parameters will determine the contraction of the lattice parameter of Pt, and in turn allow control of the electrocatalytic activity. Of equal importance will be the size of the central cavity, the number of Pt monolayers contained in the shell, and the outer diameter of the “hollow” Pt nanocrystallites.

The electrocatalytic activity of the synthesized nanoparticles will be investigated in the oxygen reduction reaction, which is the reaction that controls the electrical performance in PEMFCs. The robustness of the “hollow” Pt/C nanocrystals will be investigated in various operating conditions mimicking dynamic operating conditions of a PEMFC, in collaboration with the industrial partner Solvicore.

The experimental results will be combined with molecular dynamics simulations to describe the interatomic diffusion of M atoms and density functional theory simulations to determine the electronic properties of the final Pt-hollow nanocrystallites through collaboration with the TOP group of SIMAP (Grenoble INP-France).

Project Partners and their Role

LEPMI, Grenoble INP, France: electrochemistry, physico-chemical characterization, and up-scaling.

Applied Chemistry Department, University Liege, Belgium: synthesis of Pt@Co/C or Pt@Ni/C nanocrystallites

Industry Partner - Solvicore: integration and testing of the “hollow” nanocrystallites in real PEMFC single cells.