Mechanistic insights into atomic-to-nanoscale synergistic electrocatalysis
The integration of multi-scale active sites has emerged as a strategy to overcome intrinsic limitations of individual components in electrocatalysis. Single-atom catalysts (SACs) enable maximum atomic utilization and well-defined coordination environments, while nanoparticles/clusters (NPs/CLs) deliver superior electronic adaptability. Their synergistic combination introduces complex interfacial interactions that significantly influence reaction pathways, intermediate transport, and microenvironment modulation, yet these effects remain insufficiently understood. This review systematically analyzes recent advances of NPs/CLs-SACs in electrocatalysis, focusing on the local reaction environment and coordinating reaction pathways. NPs/CLs-SACs systems enable unique optimization of electronic structures, stabilization/transport of key intermediates, and decoupling of multi-step reaction pathways. We classify and analyze three major synergistic catalytic modes: co-adsorption catalysis, tandem catalysis, and parallel adsorption for coupling reactions. Key challenges in synthesis, stability, and mechanism understanding are identified, with future directions for rational design of sustainable catalytic technologies. The analysis draws on 76 references, including recent works on Ru/W single atoms with Pt nanoparticles for alkaline hydrogen oxidation (Nat Commun, 2025), multicomponent ensembles for oxygen reduction (Angew Chem Int Ed, 2024), and Fe–N4 sites coupled with Fe3C nanoparticles for PEMFCs (Energy Environ Sci, 2024). These studies demonstrate that precise control over atomic-to-nanoscale interfaces can yield performance metrics unattainable by single-component systems, such as enhanced CO2-to-CO electrolysis at industrial current densities and pH-universal nitrate reduction to ammonia.