Strain-Induced Corrosion Kinetics at Nanoscale Are Revealed in Liquid: Enabling Control of Corrosion Dynamics of Electrocatalysis

Abstract

Corrosion of nanoparticles during electrocatalysis, such as oxygen reduction reaction (ORR), occurs at the nanoscale and is vital for catalyst stability. Here, using liquid cell (LC) transmission electron microscopy (TEM), we study the corrosion process of palladium@platinum (Pd@Pt) core-shell octahedra in real time and reveal that both the static local strain and the evolving curvature synergistically control the nanoscale corrosion kinetics. Specifically, in locations with tensile strain and high local curvature, the etching process is much faster. Density functional theory (DFT) calculation suggests that the dissolution potential of the Pd nanocrystal decreases as the strain increases; meanwhile, Pd atoms tend to be corroded more easily on a surface under tensile strain than on one under compressive strain. With these insights on the corrosion mechanism at the nanoscale, we subsequently designed and synthesized nanoparticles with smaller strain, and these showed higher durability in both an in situ LC study and an ex situ ORR stability test.

Alloying–realloying enabled high durability for Pt–Pd-3d-transition metal nanoparticle fuel cell catalysts

“…S4j ) can be mainly attributed to realloying, which may not be associated with Cu leaching. The realloying is a slow process, causing changes of the surface sites, including the decreased hydrogen spill over as a result of the lattice strain 41 . The fact that the MA and SA increase in the first 20,000 cycles serves as a clear demonstration that activation of the catalysts originates from the dynamic dealloying–realloying process.…”

Shape Transformation Mechanism of Gallium–Indium Alloyed Liquid Metal Nanoparticles

“…[64,65] Moreover, we utilized the liquid cell in situ TEM, which enables dynamic observation of specimens in liquid environment. [66][67][68][69][70][71] It has been widely applied to fields like monitoring the nucleation and growth of NPs, [72,73] investigating the reactions on the interface of nanomaterials, [67,[74][75][76][77] and so on. Aqueous EGaIn@NBT NPs were injected into a cavity of 500 nm in height, which was sandwiched between the electrontransparency membranes (SiN x ) ( Figure 5c).…”

Alloying–Realloying Enabled High Durability for Pt–Pd–3d-Transition Metal Nanoparticle Fuel Cell Catalysts

“…4j) can be mainly attributed to realloying, which may not be associated with Cu leaching. The realloying is a slow process, causing changes of the surface sites, including the decreased hydrogen spill over as a result of the lattice strain 35 . The subtle decreases of MA and SA start after 20,000 cycles likely reflects a combination of the slow realloying process, the electrochemically-induced NP agglomeration and surface poisoning ( Fig.…”