Electrochemiluminescence Illuminates Single-Atom Catalysts: Real-Time Atomic-Scale Dynamics and Operando Electronic Fingerprinting.

Single-atom catalysts (SACs) provide atomically defined active centers for mechanistic electrocatalysis; however, their working-state structural evolution remains difficult to resolve because most characterization techniques provide either static snapshots or ensemble-averaged information. Electrochemiluminescence (ECL) has emerged as an operando optical transduction strategy that converts interfacial electron transfer and intermediate chemistry into potential-, time-, spectrally, and spatially resolved photon signals. In this Review, ECL is treated not merely as a signal-amplification phenomenon but as a structure-informative probe for single-atom catalysis. This Review first establishes a signal-conversion framework linking active-site structure, oxygen-intermediate chemistry, and photon emission. It then discusses the ability of ECL to enable the readout of active-site identity, site density, coordination configuration, electronic and spin structure, reaction intermediates, and catalytic heterogeneity, with emphasis on recent advances in potential-resolved ECL, time-dependent ECL, super-resolution ECL microscopy, and multimodal operando analysis. Finally, the key challenges in transforming ECL from a qualitative reporter into a quantitative operando structural tool are outlined. Overall, ECL is positioned as a promising bridge between static atomic structure and dynamic catalytic function in SAC research.