In-Situ monitoring intermediate stages in ammonia oxidation reaction via high performance NiCuBO_x-1/NF electrocatalysts

Oxidization of ammonia into nitrogen gas (N₂) has generated broad scientific attention in relation to the heterogeneous fixation process of N₂ and ammonia utilization as an energy carrier. Here, we report that the dendrite-like boron-doped NiCu oxide electrocatalyst over nickel foam (NiCuBO/NF) can effectively catalyze ammonia oxidation to N₂ at room temperature and ambient pressure. The required ammonium oxidization reaction (AOR) potentials and Tafel slope of Ni₄Cu₁BO_x-1/NF (NiCuBO/NF-1) electrocatalyst are 1.301 V vs RHE (at 25 mA cm⁻²) and 63 mV dec^-1, respectively. Moreover, it shows excellent AOR stability at 100 mA cm⁻² current density for 24 h. In-situ electrochemical Raman investigation demonstrates that the formation of NiOOH provides active sites on the surface of the NiCuBO electrocatalyst during AOR. Gas chromatography (GC) analysis of generated gas in the electrochemical cell at different potentials shows that the N₂ is generated from ammonia. Based on the experimental findings, we propose the possible reaction pathways for AOR. Besides this, in a two-electrode system (NiCuBO/NF-1‖ NiCuBO/NF-1), the overall ammonia splitting potential (OAS) required to reach 10 mA cm⁻² is only 1.56 V, which is dramatically less than the required potential for overall water splitting (OWS). The results shed a light for the importance of engineering a non-noble bimetallic electrocatalyst and take a great step for efficient electrooxidation of ammonia.