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

Understanding catalyst dynamics requires tracking three-dimensional atomic-scale structural evolution through full catalytic cycles. However, directly visualizing this process for individual nanocatalysts has not been achieved. Here we develop four-dimensional (4D) electrocatalytic atomic-resolution electron tomography to precisely track the 3D atomic rearrangements of individual Pd-Pt nanoparticles throughout the electrochemical cycles. We quantify the atomic dynamics and confirm two key evolutionary stages, surface reconstruction and atom leaching, corroborating with the voltage-dependent behaviors. By quantifying facet-dependent chemical short-range order and redistribution, we identify a competition between two driving forces: the electrochemical potential driving leaching and the surface energy driving inward diffusion, which dictates the final anisotropic structure. These findings demonstrate that 4D atomic perspectives are essential to decipher degradation mechanisms and to rationally design durable catalysts. The methodology offers a general platform for visualizing atomic dynamic processes at solid-liquid interfaces, opening new opportunities across materials science, catalysis, and nanotechnology.