Synthesis of Metal–Nitrogen–Carbon Electrocatalysts with Atomically Regulated Nitrogen-Doped Polycyclic Aromatic Hydrocarbons

Tuning the active site structure of metal–nitrogen–carbon electrocatalysts has recently attracted increasing interest. Herein, we report a bottom-up synthesis strategy in which atomically regulated N-doped polycyclic aromatic hydrocarbons (N-PAHs) of NxC42–x (x = 1, 2, 3, 4) were used as ligands to allow tuning of the active site’s structures of M–Nx and establish correlations between the structures and electrocatalytic properties. Based on the synthesis process, detailed characterization, and DFT calculation results, active structures of Nx–Fe1–Nx in Fe1–Nx/RGO catalysts were constructed. The results demonstrated that the extra uncoordinated N atoms around the Fe1–N4 moieties disrupted the π-conjugated NxC42–x ligands, which led to more localized electronic state in the Fe1–N4 moieties and superior catalytic performance. Especially, the Fe1–N4/RGO exhibited optimized performance for ORR with E1/2 increasing by 80 mV and Jk at 0.85 V improved 18 times (compared with Fe1–N1/RGO). This synthesis strategy utilizing N-PAHs holds significant promise for enhancing the controllability of metal–nitrogen–carbon electrocatalyst preparation.