Role of Electronic Perturbation in Stability and Activity of Pt-Based Alloy Nanocatalysts for Oxygen Reduction

Abstract

The design of electrocatalysts for polymer electrolyte membrane fuel cells must satsify two equally important fundamental principles: optimization of electrocatalytic activity and long-term stability in acid media (pH <1) at high potential (0.8 V). We report here a solution-based approach to the preparation of Pt-based alloy with early transition metals and realistic parameters for the stability and activity of Pt(3)M (M = Y, Zr, Ti, Ni, and Co) nanocatalysts for oxygen reduction reaction (ORR). The enhanced stability and activity of Pt-based alloy nanocatalysts in ORR and the relationship between electronic structure modification and stability were studied by experiment and DFT calculations. Stability correlates with the d-band fillings and the heat of alloy formation of Pt(3)M alloys, which in turn depends on the degree of the electronic perturbation due to alloying. This concept provides realistic parameters for rational catalyst design in Pt-based alloy systems.

Organic-inorganic hybrid PtCo nanoparticle with high electrocatalytic activity and durability for oxygen reduction

“…6,7 Therefore, to simultaneously decrease the use of Pt and enhance the intrinsic catalytic activity, transition metals (TMs) have been alloyed with Pt to produce bimetallic PtM (where M = Co, Fe or Ni) catalysts, which can be used as cathode materials for fuel cells. [8][9][10][11][12][13][14][15][16][17][18] The TMs are incorporated into the Pt lattice during nanoparticle synthesis, which causes compressive strain in the lattice and thereby decreases the Pt lattice constant. [9][10][11][12][13][14] It is also wellknown that electrons are transferred from the TMs to the Pt owing to the difference in their electronegativities.…”

Surface segregation and oxidation of Pt3Ni(1 1 1) alloys under oxygen environment

“…In the meantime, it has been shown that reactivity of surface can be controlled by adjusting the degrees of TM metal surface segregation, based on the thermodynamics and kinetics of bimetallic systems under oxygen exposure. Out of immense investigations, many groups in this field learn that the structure of Pt skin layer is not stable under reaction conditions and the subsurface 3d TM can be easily segregate to the surface layer under the operating conditions [5,6]. The TM has higher electronegativity than Pt and it segregates to the surface under the elevated oxygen pressure and even at low temperature, leading to the degradation of surface reactivity.…”

Carbon-Supported Ordered Pt-Ti Alloy Nanoparticles as Durable Oxygen Reduction Reaction Electrocatalyst for Polymer Electrolyte Membrane Fuel Cells

“…To overcome electrocatalyst degradation due to Pt dissolution, alloying the electrocatalyst with transition metals possessing high enthalpies of alloy formation (ΔH f ), such as Y, Sc, Zr, and Ti, has been suggested [2,3]. As the strong bonding between Pt and the transition metals hinders the removal of Pt atoms from the alloyed crystals, dissolution of Pt is expected to be suppressed when it is alloyed with transition metals having high ΔH f values.…”

“…As the strong bonding between Pt and the transition metals hinders the removal of Pt atoms from the alloyed crystals, dissolution of Pt is expected to be suppressed when it is alloyed with transition metals having high ΔH f values. To illustrate this, Yoo et al reported the preparation of thin film alloys using a sputtering technique and demonstrated that Pt alloys with Y, Zr, and Ti were resistant to degradation under ORR conditions [3][4][5]. However, in practical terms, Pt alloys with Y, Sc, or Zr cannot be utilized for application to a PEMFC cathode, as nanoparticles of Pt alloys with Y, Sc, or Zr have not been reported, and their thin films have been produced only using physical vapor deposition techniques [3][4][5].…”

“…To illustrate this, Yoo et al reported the preparation of thin film alloys using a sputtering technique and demonstrated that Pt alloys with Y, Zr, and Ti were resistant to degradation under ORR conditions [3][4][5]. However, in practical terms, Pt alloys with Y, Sc, or Zr cannot be utilized for application to a PEMFC cathode, as nanoparticles of Pt alloys with Y, Sc, or Zr have not been reported, and their thin films have been produced only using physical vapor deposition techniques [3][4][5]. To achieve both a high surface area and good electrocatalyst stability, the PEMFC cathode requires nanoparticles deposited on high-surface-area carbon supports [e.g., carbon-supported platinum nanoparticles (Pt/C)].…”