Although single-atomically dispersed metal-Nx on carbon support (M-NC) has great potential in heterogeneous catalysis, the scalable synthesis of such single-atom catalysts (SACs) with high-loading metal-Nx is greatly challenging since the loading and single-atomic dispersion have to be balanced at high temperature for forming metal-Nx. Herein, we develop a general cascade anchoring strategy for the mass production of a series of M-NC SACs with a metal loading up to 12.1 wt%. Systematic investigation reveals that the chelation of metal ions, physical isolation of chelate complex upon high loading, and the binding with N-species at elevated temperature are essential to achieving high-loading M-NC SACs. As a demonstration, high-loading Fe-NC SAC shows superior electrocatalytic performance for O2 reduction and Ni-NC SAC exhibits high electrocatalytic activity for CO2 reduction. The strategy paves a universal way to produce stable M-NC SAC with high-density metal-Nx sites for diverse high-performance applications.

Electrocatalytic N 2 reduction to NH 3 is an attractive method for artificial N 2 fixation at ambient conditions. Herein, we demonstrate that Fe-NC materials could be efficient for electrochemical N 2 reduction reaction (NRR) using iron phthalocyanine (FePc) with a well-defined FeN 4 configuration as a model catalyst. By uniformly loading FePc molecules on porous carbon, it exhibits a high electrocatalytic activity for NRR with a NH 3 yield rate of 137.95 μg h −1 mg −1 FePc at a low potential of −0.3 V (vs RHE). Importantly, by making comparisons with phthalocyanine without the Fe center and performing control and poisoning experiments together with theoretical calculations, we identify the Fe center in FeN 4 as the most active site for NRR among five possible sites in FePc and discover that the preferred route is the alternating pathway of N 2 on Fe. These results open up opportunities for further exploring metal-nitrogen-carbon materials for highly efficient electrochemical N 2 fixation and NH 3 production.