Enabling surface reconstruction through a heterostructured Ni3S4@NiCo2O4/NF towards efficient ammonia oxidation reaction

With ammonia playing a more and more vital role in serving as a renewable hydrogen carrier, it is critical to develop economical and efficient electrocatalysts for the ammonia oxidation reaction (AOR) in which hydrogen is released. In this work, a heterostructured electrocatalyst, Ni 3 S 4 @NiCo 2 O 4 /NF, was synthesized using the hydrothermal method for the purpose of improving AOR efficiency. The obtained nano catalyst exhibited an excellent AOR activity (10 mA·cm −2 at 0.58 V vs. Hg/HgO) and stability (37.2 h at 100 mA·cm −2 ). XRD and XPS characterizations indicated that the bulk catalyst remained unchanged yet with surface metallic Ni oxidized. In situ Raman spectroscopy analysis further revealed that the heterostructured catalyst underwent an obvious surface reconstruction process (Ni(OH) 2  → β-NiOOH → γ-NiOOH) which accordingly lowered the potential required for reconstruction and optimized the energy barrier for the AOR. DFT calculations showed that the heterostructured catalyst not only favors the acceleration of the reconstruction process due to electronic interactions, but also reduces the energy barrier in *NHNH 2 generation step, thus enhancing the performance of AOR, which is superior to the other two catalysts. The product gas analysis showed that the developed catalyst maintained an excellent Faraday efficiency of 95% and a continued activity. In summary, this work opened a potential new pathway for the design of heterostructured electrocatalysts for H 2 production through AOR.