Atomic-scale imaging of the growth and transformation of Pt3Ni–NiO nanoparticles

Abstract

The evolution of Pi₃Ni–NiO nanoparticles was visualized in a liquid cell. The Pt₃Ni alloy core was initially formed by a thermodynamically driven process. Next, the Ni²⁺ ions adsorbed to the Pt₃Ni nanoparticle surfaces, where they developed into Ni and then to NiO once the Pt precursor was depleted. The NiO facet transformed from (100) to (110) as the surface atoms diffused and the local kinetics varied. The interface structures of the Pt₃Ni–Ni and Ni–NiO core–shell nanoparticles were also revealed. By controlling the Ni-to-Pt ratio and tuning the electron-beam dose rates in the precursor solution, different nanoparticle types were obtained. This work might gain atomic level insights into the rational design of core–shell structures for novel catalysts.