Mechanistic insights into atomic-to-nanoscale synergistic electrocatalysis

The integration of multi-scale active sites has emerged as a promising strategy to overcome the intrinsic limitations of each individual component in electrocatalysis. While single-atom catalysts (SACs) enable maximum atomic utilization and well-defined coordination environments, nanoparticles/clusters (NPs/CLs) deliver superior electronic adaptability. However, the 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, mainly including 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, including co-adsorption catalysis, tandem catalysis, and parallel adsorption for coupling reactions. Finally, we identify key challenges in synthesis, stability, and mechanism understanding, while outlining future directions for the rational design of sustainable catalytic technologies.