Cross-Dimensional Coupled Atomic Insights Into Structural Degradation of Pt-Alloy Oxygen Reduction Reaction Catalysts.

Achieving an atomic-scale comprehensive understanding is crucial for the decipherment of nanocatalyst degradation pathways​ and guidance in rational design of durable catalysts. In this work, cross-dimensional coupled atomic-scale structural degradation mechanism of representative compound PtZn nanoalloy during oxygen reduction reaction electrocatalysis was comprehensively interrogated by integrating the atomic electron tomography (AET), synchrotron x-ray techniques, and theoretical calculations. In situ x-ray measurements demonstrated a globally stable face-centered tetragonal bulk structure during continuous cycling; at the real three-dimensional atomic level, further AET observations revealed significant localized surface degradation characterized by inhomogeneous Pt segregation, lattice transition, bond length expansion, coordination number reduction, and increased normal strain. These synergistic experimental results demonstrate a phenomenon of inhomogeneous structure degradation, revealing how dynamic interfacial change and bulk lattice stability propagate localized compositional heterogeneity: significant guidance to synthesize defect-tolerant Pt skin against Zn dissolution. Corroborated by theoretical calculations, our findings established that the Pt segregation and structural transformation on the surface and sub-surface of the catalyst were the energy-driven degradation pathways and played important roles in the sustained deactivation of the catalyst. By integration of cross-dimensional information, we link surface atomic heterogeneity on the surface of individual particles, overall structural changes of the catalyst and catalytic performance.