Fig. 1: Atomic-resolution observation of the LMSI of NiFe-Fe₃O₄ catalyst.

a–f Time-sequence HRTEM images of a NiFe-Fe₃O₄ nanoparticle under hydrogen oxidation reaction at 700 °C from Supplementary Movie 2, showing surface-diffusion-induced migration of the NiFe nanoparticle, along with the layer-by-layer reduction of Fe₃O₄. g FFT pattern of a illustrating the epitaxial relationship between the NiFe and Fe₃O₄, i.e., NiFe \((1\bar{1}2)\) // Fe₃O₄ \((1\bar{1}\bar{1})\) and NiFe [110] // Fe₃O₄ [110]. h is an enlarged image of a selected region in (a). In comparison, a simulated HRTEM image is also shown. i–n Observed layer-by-layer growth of Fe₃O₄ at the surface of Fe₃O₄ from Supplementary Movie 3. o Schematic image illustrates the relation between the LMSI effect and catalytic reactions. The reduction of Fe₃O₄ at the NiFe-Fe₃O₄ interface resulted in the migration of the interface. Additionally, the oxidation of Fe at the edge sites of the Fe₃O₄ {111} planes leads to the growth of Fe₃O₄.