Atomic catalysts have become a promising area in electrocatalysis due to their high efficiency and selectivity. This review discusses the structural engineering of atomic catalysts for various electrocatalytic reactions, including the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), carbon dioxide reduction reaction (CO₂RR), and nitrogen reduction reaction (NRR). The review highlights the importance of geometric and electronic structure regulation of metal active centers, as well as the synergistic effects, defect-induced spin state changes, and crystal field distortion in enhancing catalytic performance. Challenges in optimizing atomic catalysts include controlled synthesis, increasing active site density, enhancing intrinsic activity, and improving stability. The review also discusses the structure-function relationships of atomic catalysts in these reactions and proposes technical challenges and research directions for developing high-performance atomic catalysts. The review emphasizes the role of substrates, central metal atoms, and coordination environments in determining catalytic activity. It also discusses the development of single-atom catalysts (SACs), diatomic catalysts (DACs), and triatomic catalysts (TACs), highlighting their unique properties and potential applications. The review provides insights into the design and optimization of atomic catalysts for electrocatalytic applications, emphasizing the importance of understanding the electronic structure and coordination environment of active sites. The review also discusses the potential of atomic catalysts in reducing the reliance on precious metals and improving the efficiency and sustainability of electrocatalytic processes.Atomic catalysts have become a promising area in electrocatalysis due to their high efficiency and selectivity. This review discusses the structural engineering of atomic catalysts for various electrocatalytic reactions, including the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), carbon dioxide reduction reaction (CO₂RR), and nitrogen reduction reaction (NRR). The review highlights the importance of geometric and electronic structure regulation of metal active centers, as well as the synergistic effects, defect-induced spin state changes, and crystal field distortion in enhancing catalytic performance. Challenges in optimizing atomic catalysts include controlled synthesis, increasing active site density, enhancing intrinsic activity, and improving stability. The review also discusses the structure-function relationships of atomic catalysts in these reactions and proposes technical challenges and research directions for developing high-performance atomic catalysts. The review emphasizes the role of substrates, central metal atoms, and coordination environments in determining catalytic activity. It also discusses the development of single-atom catalysts (SACs), diatomic catalysts (DACs), and triatomic catalysts (TACs), highlighting their unique properties and potential applications. The review provides insights into the design and optimization of atomic catalysts for electrocatalytic applications, emphasizing the importance of understanding the electronic structure and coordination environment of active sites. The review also discusses the potential of atomic catalysts in reducing the reliance on precious metals and improving the efficiency and sustainability of electrocatalytic processes.