Highly selective and stable ammonia electro-oxidation over zirconium-promoted NiCu oxide nanosheets

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Realizing efficient ammonia electro-oxidation reactions (AOR) under mild conditions is of broad interest for ammonia reforming to hydrogen and direct ammonia fuel cells; however, the development of low-cost, earth-abundant AOR electrocatalysts remains challenging. Herein, we report Ni 3 Cu 1 Zr 0.5 /C, a non-precious metal-based nanocatalyst comprised of 2–3 nm-thick zirconium-promoted NiCu oxide nanosheets grown in situ on approximately 20 nm carbon black, for highly efficient AOR in alkaline media. Zirconium incorporation induced a pronounced structural reconstruction from unconsolidated nanorods into a nanosheet network, leading to enhanced Ni-Cu catalytic cooperation and a substantially enlarged active surface area. Consequently, the optimized catalyst delivered a peak current density of 138 mA cm –2 at 0.65 V versus Hg/HgO in 1 M KOH with 0.1 M NH 3 , exhibiting a dominant NO x /NO x – Faradaic efficiency of 91.8%, which increased to 284 mA cm –2 under 0.3 M NH 3 , markedly outperforming the Zr-free Ni 3 Cu 1 /C counterpart. Ni 3 Cu 1 Zr 0.5 /C also exhibited accelerated reaction kinetics, a lower apparent activation energy, and enhanced stability, sustaining only an 8.7% current decay over 18,000 s. Kinetic analysis revealed a stronger OH – dependence after Zr incorporation, and molecular-level electrochemical in situ attenuated total reflectance surface-enhanced infrared absorption spectroscopy combined with online differential electrochemical mass spectrometry supported that the accelerated interfacial hydroxyl turnover promoted sequential NH 3 oxidation toward N 2 O/NO, NO 2 – , and NO 3 – products. These final products are attractive for nitrogen valorization while simultaneously releasing more electrons per ammonia molecule. This study highlights promoter-enabled interfacial engineering as an effective strategy for advancing non-noble-metal catalysts for AOR toward clean energy applications.

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