Single−atom catalysts (SACs) have attracted significant attention in the field of electrocatalytic energy conversion owing to their unique catalytic properties and exceptionally high metal−atom utilization efficiency. This review systematically summarizes recent synthesis strategies for SACs, and critically analyzes the advantages and limitations of each approach. With respect to catalyst characterization, advanced techniques, such as aberration−corrected scanning transmission electron microscopy (AC−STEM) and X − ray absorption fine structure (XAFS), are highlighted for their crucial roles in elucidating atomic dispersion, coordination environments and electronic structures. Furthermore, the performance and applications of SACs in key electrocatalytic reactions are comprehensively reviewed, including the oxygen reduction reaction (ORR), hydrogen evolution reaction (HER), and other representative reactions. Finally, current challenges and future research directions are discussed, offering insights into the reasonable design of high−performance SACs and their progress towards practical applications.

Recent advances in synthesis strategies and electrocatalytic applications of single−atom catalysts
    Abstract
    Article highlights
    1 Introduction
    2 Synthesis strategies of sacs
        2.1 Wet−chemical methods
            2.1.1 Impregnation method
            2.1.2 Coprecipitation method
    2.2 Chemical deposition methods
        2.2.1 Atomic layer deposition
        2.2.2 Chemical vapor deposition
    2.3 Pyrolysis method
    2.4 Ball milling
    2.5 Photochemical reduction method
    3 Characterization of single−atom catalysts
        3.1 Aberration−corrected scanning transmission electron microscopy
        3.2 X−ray absorption fine structure
        3.3 In situ techniques
            3.3.1 In situ FTIR
            3.3.2 In situ Raman
    4 Theoretical prediction
    5 Electrocatalytic applications of single−atom catalysts
        5.1 Oxygen reduction reaction (ORR)
        5.2 Hydrogen evolution reaction (HER)
        5.3 Oxygen evolution reaction (OER)
        5.4 Carbon dioxide reduction reaction (CRR)
        5.5 Nitrogen reduction reaction (NRR)
    6 Conclusion and outlook
        6.1 Conclusion
        6.2 Outlook
    References

• Liang Chen(Key Laboratory of Hunan Province for Advanced Carbon‒based Functional Materials, School of Chemistry and Chemical Engineering, Hunan Institute of Science and Technology, Yueyang 414006, Hunan, China) Corresponding author
• Qing Zeng(Key Laboratory of Hunan Province for Advanced Carbon‒based Functional Materials, School of Chemistry and Chemical Engineering, Hunan Institute of Science and Technology, Yueyang 414006, Hunan, China)
• Yun Peng(Key Laboratory of Hunan Province for Advanced Carbon‒based Functional Materials, School of Chemistry and Chemical Engineering, Hunan Institute of Science and Technology, Yueyang 414006, Hunan, China)
• Gangyong Li(Key Laboratory of Hunan Province for Advanced Carbon‒based Functional Materials, School of Chemistry and Chemical Engineering, Hunan Institute of Science and Technology, Yueyang 414006, Hunan, China)
• Wei Wang(Key Laboratory of Hunan Province for Advanced Carbon‒based Functional Materials, School of Chemistry and Chemical Engineering, Hunan Institute of Science and Technology, Yueyang 414006, Hunan, China)
• Zhaohui Hou(Key Laboratory of Hunan Province for Advanced Carbon‒based Functional Materials, School of Chemistry and Chemical Engineering, Hunan Institute of Science and Technology, Yueyang 414006, Hunan, China)
• Chenxi X. Xu(School of Chemistry and Chemical Engineering, Central South University of Forestry and Technology, Changsha 410004, Hunan, China)
• Yucan Zhu(College of Mechanical Engineering, Hunan Institute of Science and Technology, Yueyang 414006, Hunan, China)
• Jiale Sun(Institute of Intelligent Innovation, Henan Academy of Sciences, Zhengzhou, Henan 451162, China)