Structural Degradation of M–N–C (M=Co, Ni and Fe) Single‐Atom Electrocatalysts at Industrial‐Grade Current Density for Long‐Term Reduction

M‐N‐C single‐atom catalysts (SACs) are promising electrode materials for many electro‐reduction reactions. However, their stability is far from practical applications, and their deactivation mechanism has been rarely investigated. Herein, we demonstrate the structural degradation of M‐N‐C (M=Co, Ni, and Fe) at industrial‐grade current density for long‐term electro‐reduction. Both M‐N and N‐C bonds are broken, resulting in the gradual hydrogenation and dissolution of N in the form of ammonia. The residual M is finally converted to M‐containing core–shell nanoparticles after sequential dissolution, redeposition, and electro‐reduction. The destruction of the M‐N‐C structure and the formation of nanoparticles greatly affect the electrocatalytic performance. Our work highlights the structural degradation and deactivation mechanism of M‐N‐C‐type SACs under strong reductive conditions and provides useful information for inspiring researchers to develop new strategies to improve the electrocatalytic stability of similar types of materials.