Tuning strain of Platinum-Cobalt-Zinc trimetallic nanoparticles for efficient oxygen reduction Catalysis.

Controlling strain in nanomaterials is a key strategy for tuning the mechanics-chemistry interaction and enhance the performance of heterogeneous catalysts. Here, we present a straightforward one-pot synthesis approach for fabricating platinum-cobalt-zinc (PtCoZn) trimetallic catalysts with adjustable Pt strain, enabling exceptional catalytic performance for the oxygen reduction reaction (ORR), comparable to that of state-of-the-art Pt-based alloy catalysts. With increasing the contents of Co and Zn, transmission electron microscope (TEM) reveals that the lattice spacings decreases from 2.26 Å for Pt to 2.19 Å for PtCoZn. This indicates that the addition of Zn and Co induces compressive strain in Pt, a finding further corroborated by extended X-ray adsorption fine structure (EXAFS). PtCoZn with a lattice space of 2.23 Å exhibits the optimum performance, achieving a mass activity (MA) of 3.25 A/mg and a specific activity (SA) of 7.57 mA/cm, which are 4.3 times and 7 times higher than those of the commercial Pt/C catalyst, respectively. Moreover, the catalyst demonstrates robust electrochemical durability with negligible activity degradation after 50,000 cycles. The catalytic mechanism is elucidated through in situ electrochemical reflection Fourier transformed infrared (FTIR) and density functional theory (DFT) calculations. The compressive strain in Pt, which weakens the binding strength of oxygen intermediates and enhances ORR activity, is primarily induced by the incorporation of Zn. Meanwhile, Co doping suppresses Zn leaching and improves the stability of PtCoZn by anchoring Zn atoms within the inner layers of the alloy particles. This work sheds new light on developing catalysts through strain engineering in multimetallic systems.