In-Situ monitoring intermediate stages in ammonia oxidation reaction via high performance NiCuBOx-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 Ni4Cu1BOx-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.