Preparation of nickel-copper layered double hydroxide on nickel foam as a non-noble catalyst for efficient electrooxidation of ammonia

Electrochemical oxidation of ammonia is an energy-effective and environment-friendly technology for ammonia-containing wastewater treatment. The key challenge is to explore the high activity and low-price catalyst for ammonia electrooxidation. NiCu layered double hydroxide (NiCu-LDH) on nickel foam (NF) was synthesized for ammonia oxidation via a facile hydrothermal reaction. The Ni0.9Cu0.1-LDH/NF achieved a maximum current density of 78 mA·cm−2 at 1.76 V vs. RHE and a lowest Tafel slope of 195.64 MV·dec−1 in comparison with other catalysts, which was prepared by using different molar ratios of Ni2+ and Cu2+. The Ni0.9Cu0.1-LDH/NF showed smaller and denser nanosheets compared with that of Ni(OH)2/NF, indicating it had more electrochemical active areas and active sites. Chronoamperometry tests showed that the Ni0.9Cu0.1-LDH /NF reached a current density of 23 mA·cm−2 after 120 mins, which was four times as high as Ni(OH)2/NF (6 mA·cm−2). The above results demonstrated that incorporating Cu into the Ni-based layered hydroxides could improve the electrochemical activity of the catalyst, showing Ni0.9Cu0.1-LDH /NF to be a prospective inexpensive, and steady catalyst for high-performance of ammonia electrooxidation.