Tracking four-dimensional atomic evolutions of single nanocatalysts throughout the life cycles

Abstract: Structural changes induced by chemical reactions critically determine the catalytic performance and mechanism. However, precise tracking of the three-dimensional (3D) atomic structural evolution of individual bimetallic nanocatalysts remains challenging. Here we develop four-dimensional electrocatalytic atomic-resolution electron tomography, a method for directly tracking 3D atomic rearrangements in identical nanoparticles by electrocatalytic reactions. Using Pd-Pt bimetallic nanoparticles as a model system, we capture the atomic evolution of single nanocatalysts throughout electrocatalytic cycles. We observe two stages of evolutions: surface reconstruction and atom leaching, which are corroborated with the voltage-dependent behaviors probed by in situ electrochemical transmission electron microscopy. We identify chemical short-range order at atomic level and further reveal anisotropic chemical redistributions across different crystallographic orientations. These findings highlight the necessity of incorporating 3D spatiotemporal and chemical evolutions into the rational design of functional nanocatalysts in the future.