Metal nitride nanosheets enable highly efficient electrochemical oxidation of ammonia. (February 2021)

• Record Type: Journal Article
• Authors: He, Shi; Chen, Yufeng; Wang, Mengdi; Liu, Kai; Novello, Peter; Li, Xueqian; Zhu, Siyuan; Liu, Jie
• Is Part Of: Nano energy. Volume 80(2021)
• Publication Date: 2021-02
• Subjects: Electrochemistry -- Catalysis -- Ammonia electrolysis -- Ammonia oxidation -- Hydrogen storage; Nanoscience -- Periodicals; Nanotechnology -- Periodicals; Nanostructured materials -- Periodicals; Power resources -- Technological innovations -- Periodicals; Nanoscience; Nanostructured materials; Nanotechnology; Power resources -- Technological innovations; Periodicals; 621.042
• DOI: 10.1016/j.nanoen.2020.105528
• Languages: English
• ISSNs: 2211-2855

Abstract

Abstract: Ammonia has been recognized as a promising hydrogen mediator as it reduces the expense of the long-range transportation of hydrogen. However, methods to extract hydrogen from ammonia require improvements to decrease the overall cost. Ammonia electrolysis provides a convenient method to attain a low-cost hydrogen production. Here, we report that nickel-cobalt nitride nanosheets can achieve high electrocatalytic activity for the ammonia oxidation reaction (AOR) in non-aqueous solutions. The AOR onset overpotential of NiCo2 N nanosheets is 0.55 V, which is about 0.25 V lower than that of the Pt/C electrocatalyst. Our ultraviolet–visible and mass spectroscopy studies reveal that NiCo2 N nanosheets bypass the formation of the soluble metal-amine complex and preferentially oxidize ammonia to environmentally friendly diatomic nitrogen with a Faradic efficiency of over 90%. Theoretical simulation further indicates that the downshift of metal d-band on NiCo2 N nanosheets surface helps retain a long-lasting electrocatalytic activity. Overall, this work introduces a new family of active and stable electrocatalysts for AOR that is based on earth-abundant transition metals, heralding the feasibility of using ammonia as a hydrogen mediator in hydrogen-based applications. Graphical Abstract: ga1 Highlights: Metal nitride nanosheets were promising catalysts for efficient electrochemical ammonia oxidation. The optimized NiCo2 N nanosheets showed highest activity for ammonia electrochemical oxidation in acetonitrile solution. The corrosion of the catalysts was suppressed by the formation of strong metal nitrogen chemical bonds in the catalysts. Moderate d-band center of the NiCo2 N nanosheets boosts ammonia electrochemical oxidation toward N2 .