Edge-rich carbon-based single-atom catalysts: Recent progress and critical contributions to electrocatalytic applications

Amid the global push for energy transition and carbon neutrality, constructing highly active electrocatalysts is essential to overcome the challenges of energy conversion and storage. N-doped carbon substrate-based single-atom catalysts (SA/NCs), with a clear reaction center, robust stability, and excellent electrical conductivity, have emerged as a key focus in electrocatalytic research. However, traditional SA/NCs mainly exhibit a porphyrin-like planar M–N4 configuration, with a symmetrical charge distribution that limits their catalytic efficiency. Recently, the development of edge-rich NC substrates to anchor edge-type metal sites (eSA/NCs) can induce charge rearrangement and promote the exposure of active sites, leading to significantly enhanced electrocatalytic performance. This review provides a comprehensive summary of eSA/NCs for electrocatalytic reactions. First, the synthetic strategies of eSA/NCs are classified, and the main characterization techniques are introduced. Subsequently, the performance of eSA/NCs in diverse electrocatalytic reactions is carefully discussed, with emphasis on elucidating the structure-activity relationships underpinned by edge structure. Finally, regarding the issues of controllable construction and quantitative analysis of the current NC substrates with high edge density, we have proposed feasible development directions and strategies. This work highlights the significance of edge structure contributions in enhancing the catalytic efficiency of SA/NCs and provides technical guidance for designing future high-performance electrocatalysts.