Cascade Synthesis of Intermetallic PtZn Electrocatalysts for Practical Fuel Cells

Abstract

The performance of Pt-based intermetallic electrocatalysts for the oxygen reduction reaction in practical fuel cells can be substantially enhanced via the phase engineering-based regulation of strain effects. Herein, cascade synthesis exploiting a temperature-dependent phase evolution process is used to prepare L10-PtZn intermetallic compounds. ZnS produced in situ as an intermediate is shown to induce a sequential transformation of Pt to L12-Pt3Zn and L10-PtZn upon annealing. The resulting core/shell PtZn/Pt catalysts demonstrate a high mass activity of 1.18 A mgPt −1 at 0.9 V in a half-cell test and a high current density of 0.98 A cm−2 at 0.7 V in a fuel-cell test, experiencing a voltage drop of only 23 mV after 30 000 voltage cycles at 0.8 A cm−2. Density functional theory calculations and experiments indicate that the high activity of these catalysts is due to the strain effect caused by the lattice mismatch between the PtZn core and Pt (110) skin (and not Pt (111)). This study underscores the strategic use of phase-engineering-driven strain regulation in the design of high-performance Pt-based electrocatalysts for energy conversion applications.