Electrooxidation of ammonia on A-site deficient perovskite oxide La_0.9Ni_0.6Cu_0.35Fe_0.05O _3-d for wastewater treatment

Wastewater can contain high amounts of ammonia which can pose as a great safety threat if released into natural waters. The electrochemical oxidation of ammonia offers a viable strategy to remove high concentrations and provides an attractive method for wastewater treatment. However, finding a highly efficient and low-cost catalyst is imperative for overcoming the sluggish nature of ammonia oxidation reaction. Herein, a modified A- and B-site perovskite is proposed as a catalyst for the oxidation of ammonia, making it suitable as an anode in an ammonia electrolyser. A series of La1-yNi0.6Cu0.4-xFexO3-delta (x = 0, 0.05 and 0.10; y = 0, 0.05 and 0.10) perovskite materials were synthesised by a conventional sol-gel method. Amongst those tested oxides, La0.9Ni0.6Cu0.35Fe0.05O3-delta was found to have superior activity towards the electrooxidation of ammonia due to an optimised amount of Fe doping and the presence of oxygen vacancies introduced by an A-site deficiency. Subsequently, La0.9Ni0.6Cu0.35Fe0.05O3-delta was employed as an anode in an ammonia electrolyser where the ammonia removal efficiency reached 95.4 % in simulated wastewater after 80 hr and a substantial reduction in real wastewater was also observed. These results demonstrate that the A-site deficient perovskite materials are a viable electrode for the removal of ammonia in a practical energy setting and paves way for future applications.