Heterogeneous Corrosion Pathways in Pt-Ni Nanododecahedra Revealed by In Situ Liquid Cell TEM

Unraveling nanoscale corrosion pathways is essential for understanding materials degradation mechanisms and designing corrosion-resistant metal alloys. Here, we directly visualize the corrosion of Pt-Ni nanododecahedra in 0.1 M HCl using liquid cell TEM. Each nanoparticle features a Ni-rich core and a Pt-rich frame. Our observation reveals that corrosion proceeds in two distinct stages: first the Ni-rich core dissolves without forming porosity, yielding small Pt nanocrystals and transient NiCl₂·6H₂O at the retreating interfaces; then the Pt-rich frame fragments into ∼5 nm Pt₃Ni nanocrystals that subsequently dissolve uniformly, accompanied by fleeting Pt chlorides. A percolation-based theory explains the observed behaviors: The core's ∼8% Pt lies below the Pt connectivity threshold, preventing Pt scaffold formation, whereas the frame's 48% Ni exceeds the Ni percolation threshold and collapses. Ordered Pt₃Ni suppresses Ni percolation, thereby enforcing uniform dissolution. These findings reveal how composition and structural ordering govern heterogeneous corrosion in Pt-Ni architectured nanoparticles.