Transition Metal Nanoparticle-Embedded Nitrogen-Doped Carbon Nanorods as an Efficient Electrocatalyst for Selective Electroreduction of Nitric Oxide to Ammonia

The electrochemical reduction of nitric oxide reaction (eNORR) has gained huge attention due to its ecological approach to producing NH₃. We explored various transition metal (TM) active sites (Fe, Co, Ni, Cu, and Zn) with nitrogen heteroatoms in one-dimensional (1D) carbon nanorods to unveil the performance of these candidates in facilitating the electrosynthesis of NH₃ via eNORR. Remarkably, Ni nanoparticle-embedded nitrogen-doped carbon nanorods (Ni-NCNR) exceeded other TM-NCNR catalysts in terms of NH₃ faradaic efficiency (FE_NH3) and NH₃ yield rate. Furthermore, we addressed the effect of graphitization, porosity, and N-heteroatom doping on eNORR by the strategic design of various Ni-NCNR and systematic control experiments. Above all, Ni-NCNR700 secured the highest FE_NH3 of 85.5 ± 0.8% at a low overpotential of 610 mV with a substantial NH₃ yield rate of 23.8 ± 2.6 μmol cm^-2 h^-1. The Ni-NCNR700 electrocatalyst showed a robust performance in cyclability and 24 h long-term stability tests. Our analysis reveals that for an efficient eNORR to NH₃, the selection of suitable active sites with pertinent tuning is crucial.