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-N-x and establish correlations between the structures and electrocatalytic properties. Based on the synthesis process, detailed characterization, and DFT calculation results, active structures of Nx-Fe-1-Nx in Fe-1-Nx/RGO catalysts were constructed. The results demonstrated that the extra uncoordinated N atoms around the Fe-1-N-4 moieties disrupted the pi-conjugated NxC42-x ligands, which led to more localized electronic state in the Fe-1-N-4 moieties and superior catalytic performance. Especially, the Fe-1-N4/RGO exhibited optimized performance for ORR with E-1/2 increasing by 80 mV and J(k) at 0.85 V improved 18 times (compared with Fe-1-N1/RGO). This synthesis strategy utilizing N-PAHs holds significant promise for enhancing the controllability of metal-nitrogen-carbon electrocatalyst preparation.