Revealing the atomic ordering of binary intermetallics using in situ heating techniques at multilength scales

Abstract

Significance We present a comprehensive quantitative study of the dynamic order–disorder phase transition of Pt 3 Co nanoparticles, binary intermetallic oxygen-reduction reaction fuel cell electrocatalysts, during postsynthesis annealing. We employed in situ synchrotron-based X-ray diffraction (XRD) and in situ scanning transmission EM (STEM) to study the phase transition and morphological and structural changes during real-time annealing. In situ XRD revealed the impact of annealing/cooling conditions on the degree of ordering, particle size and lattice strain. In situ heating STEM enabled visualization of nanoparticle migration and growth. We find that a higher degree of ordering leads to more active and durable electrocatalysts. Our findings represent a groundbreaking advance in electrocatalyst development/design with a broad impact on energy materials, in general, and fuel cells, in particular.