Synergistic catalysis, through cooperative effects between two active sites or among multiple active sites, can efficiently drive multi-step complex reactions, and bifunctional or multifunctional active sites have been established on homogeneous and heterogeneous catalysts. A profound understanding of the synergistic mechanisms of these catalysts is crucial for achieving rational catalyst design and high-performance regulation. Accordingly, the article highlights the application of increasing scales of metal active sites (single-atom catalysts, dual-atom catalysts, metal clusters, and nanoparticles) in the electrocatalytic nitrate reduction reaction, given that this reaction involves a complex network featuring multiple proton-electron transfer steps and a variety of reaction intermediates. Finally, future design directions for synergistic catalysts are envisaged, aiming to provide insights for developing highly efficient ammonia synthesis catalysts and theoretical references for elucidating the essence of synergistic catalysis.



