Microwave Regenerable Nickel, Zinc Co-doped Nitrogen-Coordinated Porous Carbon Catalyst for Nitrogen Fixation

Abstract

More than 90% of the global NH₃ synthesis is dominated by the Haber-Bosch process, which consumes 2% of the worldwide energy and generates 1.44% of the global carbon emission. The electrochemical N₂ reduction reaction (NRR) is regarded as an attractive alternative route to produce NH₃ under mild reaction conditions, but the electrocatalysts suffer from the difficulty of N≡N cleavage. In this work, we report a leaf-like MOF-derived Ni/Zn bimetallic co-doped nitrogen-coordinated porous carbon (Ni/Zn-NPC) as a cost-effective NH₃ synthesis electrocatalyst. The resultant electrocatalyst achieved a high NH₃ production rate of 22.68 μg h^-1 mg_cat^-1 at -1.0 V vs a reversible hydrogen electrode (RHE) in a 0.1 M Na₂SO₄ electrolyte. The Ni/Zn-NPC material can be called a microwave regenerable catalyst because microwave treatment has proven to be a crucial part of the multi-field coupling to detoxify and make the catalyst reactive, further improving its stability. Density functional theory (DFT) was chosen to explore the mechanism of Ni/Zn-NPC for NRR, providing a profound prediction of the structure of the active site and related reaction pathways and revealing that trace Ni doping optimizes the local coordination environment and N₂ adsorption of Zn atoms.