Rationally
designing the core/shell architecture of Pt-based electrocatalysts
has been demonstrated as an effective way to induce a surface strain
effect for promoting the sluggish kinetics of the oxygen reduction
reaction (ORR) at the cathode of fuel cells. However, unstable core
dissolution and structural collapse usually occur in Pt-based core/shell
catalysts during the long-term cycling operation, greatly impacting
actual fuel cell applications. Impeding the dissolution of cores beneath
the Pt shells is the key to enhancing the catalytic stability of materials.
Herein, a method for sandwiching atomic PdAu interlayers into one-dimensional
(1D) Pd/Pt core/shell nanowires (NWs) is developed to greatly boost
the catalytic stability of subnanometer Pt shells for ORR. The Pd/PdAu/Pt
core/shell/shell NWs display only 7.80% degradation of ORR mass activity
over 80 000 potential cycles with no dissolution of Pd cores
and good preservation of the holistic sandwich core/shell nanostructures.
This is a significant improvement of electrocatalytic stability compared
with the Pd/Pt core/shell NWs, which deformed and inactivated over
80 000 potential cycles. The density functional theory (DFT)
calculations further demonstrate that the electron-transfer bridge
Pd and electron reservoir Au, serving in the PdAu atomic interlayer,
both guarantee the preservation of the high electroactivity of surface
Pt sites during the long-term ORR stability test. In addition, the
Pd/PdAu/Pt NWs show a 1.7-fold higher mass activity (MA) for ORR than
the conventional Pd/Pt NWs. The enhanced activity can be attributed
to the strong interaction between PdAu interlayers and subnanometer-Pt
shells, which suppresses the competitive Pd-4d bands and boosts the
surface Pt-5d bands toward the Fermi level for higher electroactivity,
proved from DFT.