Microstructure determination of PdRu immiscible alloys based on electron-pair distribution function and local elemental segregation

Structural information in a disordered atomic system cannot be acquired from everyday X-ray diffractometers, so we have to resort to synchrotron resources. The pair distribution function from synchrotron X-ray and neutron scattering reflects the local bond information regardless of the crystallinity, but the limited access to these high-energy light resources prevents them from widespread use. Here, we develop a microstructure analysis framework to study immiscible binary alloys through the integration of local elemental segregation analysis, electron-based pair distribution function, the corresponding wavelet coherence spectrum, and ab initio level simulation. All the information can be obtained from an in-house transmission electron microscope equipped with an energy-dispersive spectroscope. A series of nanoparticles based on immiscible Pd-Ru alloys are chosen as model catalysts for the hydrogen evolution reaction, and the structure-performance relationship is established on the basis of the electrochemical tests and structural information from the analysis toolkit we developed.