Pseudotime uncovers restructuring dynamics and mitigators of metal catalyst deactivation.

Structural reconstruction is a major cause of heterogeneous catalyst deactivation, yet elucidating the restructuring mechanism remains difficult due to underresolved dynamics. Here, by introducing pseudotime, we recover dynamics and identify the key determinant of nanoparticle sintering from ex situ electron microscopy alone, beyond the general view that postmortem observations provide only end-state structures. Pseudotemporal ordering of SiNx-supported gold across asynchronous aging states reveals that interparticle distance controls stability against migration and coalescence, with a well-defined threshold quantified. In situ gas cell tracking validated this threshold with only a 2-angstrom deviation and confirmed markedly suppressed particle mobility beyond it, allowing sintering prediction with 92% accuracy, thereby establishing proximity as a quantitative handle for improving sinter resistance. The proximity effect resolved here illustrates pseudotime as a new lens for understanding time-resolved phenomena in catalysis, opening the possibility of probing the restructuring dynamics beyond in situ or operando characterizations.