Thermally induced surface-Cu-enriched NiCuOx electrocatalysts for stable ammonia oxidation to nitrite toward hydrogen production

초록

Nitrites are crucial for various industries, including fertilizers and the food industry. However, the traditional thermochemical Ostwald process requires high energy consumption and entails nitrogen loss. Ammonia electrolysis can produce nitrogen with a low theoretical thermodynamic potential of 0.06 V and nitrite at a higher anodic potential at room temperature and ambient pressure. To compete with the existing nitrite synthesis methods, developing electrocatalysts with high catalytic activity and stability is of prime interest for industrial applications. In this study, we explore the design strategy of bimetallic catalysts for converting ammonia into nitrites based on the *N binding energy of metal. Based on the density function theory (DFT) calculations, we investigate the effects of Ni-M catalysts synthesized by the facile electrodeposition method on catalytic activity and stability of the ammonia oxidation reaction. To overcome the stability of Ni-Cu electrocatalysts, we form surface-Cu-enriched NiCuOx catalysts via thermal annealing for converting ammonia into nitrites. Surface-Cu-enriched NiCuOx prevents corrosion of the catalysts in alkaline media with the presence of ammonia while maintaining the ammonia-to-nitrite formation properties. This research contributes to the design strategy of catalysts through simple and energy-efficient synthesis methods and an understanding of ammonia electrooxidation mechanisms.

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