Enhanced ammonia yield rate from nitrogen on collapsed dodecahedral-shaped Co/NC electrocatalyst

Abstract

Nowadays, multi-component non-precious metal catalysts have been considered as a significant strategy for enhancing the yield of synthesizing NH₃ by electrocatalytic nitrogen reduction reaction (E-NRR). In the present work, carbon composites doped with well-dispersed Co and N (Co/NC) were prepared by pyrolyzing zeolitic imidazolate framework-67 (ZIF-67) at various temperatures protected under a N₂ flow. Co/NC exhibits a collapsed dodecahedral morphology with a mesoporous structure (3.5-4 nm). The chemical states of Co/N and the structural defects of C are closely related to the carbonization temperature. In a N₂-saturated 0.1 M KOH electrolyte, the as-prepared catalysts exhibit an NH₃ yield rate (Y(NH₃)) of 60.57 μg h^-1 mg_cat.^-1 and a Faradaic efficiency (FE) of 23.3% at -0.1 V (vs the reversible hydrogen electrode, RHE) at ambient conditions. The enhanced E-NRR activity of Co/NC may primarily originate from an associative distal pathway on the Co-N₃-C sites and the carbon defects in an alkaline electrolyte. Specifically, this work presents a three-component E-NRR catalyst with excellent stability and great activity based on Co/NC.