Dual-atom catalysts (DACs), in which two metal atoms are anchored on a support through coordination interactions, have emerged as a new frontier in catalysis. Inheriting the advantages of single-atom catalysts (SACs), such as near 100% atom utilization and well-defined active sites, DACs also overcome the intrinsic limitations of SACs in complex reactions involving multi-electron transfer and multiple intermediates through synergistic interactions between dual metal sites. This synergy enables simultaneously optimizing the adsorption energies of different reaction intermediates, thereby breaking the scaling relations that often constrain SACs, and leading to markedly enhanced catalytic activity and selectivity. This review systematically summarizes recent progress in the development of precise synthetic strategies, characterization techniques, synergistic mechanisms, and catalytic applications of DACs. We first outline the development history of DACs over the past two decades, dividing it into three characteristic stages: conceptual exploration, rapid development, and application expansion. We then summarize state-of-the-art synthetic methods for precise construction of DACs with well-defined structures. For homogeneous DACs synthesis, macrocyclic ligand-directed synthesis enables the precise assembly of dual-atom sites with controlled metal-metal distances and coordination environments. In heterogeneous DACs synthesis, several effective strategies have been developed, including the dinuclear metal complex templating method, the photo-induced charge enrichment strategy, and the ion-exchange strategy etc., all of which enable the fabrication of DACs with high purity and tunable local structures. Following this, we introduce the main characterization techniques for DACs, with emphasis on the determination of bimetallic configurations, coordination environments, electronic structures, and in situ dynamic evolution under reaction conditions. Aberration-corrected scanning transmission electron microscopy provides direct visualization of atomic arrangements, while synchrotron-based X-ray absorption spectroscopy offers the information on local coordination geometry and oxidation states. More importantly, in situ/operando spectroscopic techniques enable real-time tracking of structural evolution during catalysis process, which is essential for understanding the real reaction mechanism. We further elucidate the mechanism of synergistic effects from both electronic and steric perspectives. The electronic effect involves charge transfer, orbital hybridization, and d-band center modulation between the two metal atoms, whereas the steric effect is governed by interatomic distance, bridging configuration, and local spatial confinement. These two effects are intimately coupled and collectively constitute the essential features that distinguish DACs from SACs. Finally, we overview their applications in oxygen reduction, CO₂ reduction, hydrogen and oxygen evolution, and provide perspectives on remaining challenges and future opportunities, aiming to offer guidance for the rational design and practical applications of DACs in sustainable energy conversion.

Key words: dual-atom catalyst, precise synthesis, structural characterization, synergistic mechanism, energy catalysis