Pb induced dislocation defects of PtCo systems: Strain-triggered oxygen reduction reaction for PEMFC

Design and development of advanced electrocatalysts with high performance and low Pt consumption are crucial for reducing the kinetic energy barrier of the cathode oxygen reduction reaction (ORR) and improving the efficiency of proton exchange membrane fuel cells (PEMFC). In this study, we demonstrate a Pb-modulated PtCo system for efficient ORR, in which the inclusion of Pb in ternary alloys induces dislocation defects due to the significant difference in atomic radius. Dislocation-PtCoPb was confirmed to exhibit significantly higher ORR activity and stability in acidic ORR. In practical PEMFC applications, it outperforms the corresponding commercial Pt/C with a mass activity of 0.58 A·mg_Pt⁻¹, making it a promising alternative to state-of-the-art Pt-based catalysts. The combination of experimental results and density functional theory (DFT) calculations offers valuable atomic-level insights into the dislocation structures. Pb with a larger atomic radius is located in the lattice stretching region below the dislocation slip plane, forming a structure similar to a Cottrell atmosphere, which reduces the dislocation energy and puts the system in a lower energy state. The Cottrell atmosphere pins the dislocation structure and stabilizes the ternary alloy. By adjusting the amount of added Pb, a moderate level of dislocation density induces a tuned strain effect, thereby enhancing the electrocatalytic mechanism by optimizing the electronic structure of the alloy surface and the adsorption and desorption of oxygen species. This work provides valuable insights into the design and development of lattice dislocation defect structures to trigger strain effects for improving ORR performance.