Enhanced Nitrite Electrovalorization to Ammonia by a NiFe Layered Double Hydroxide

Abstract

The development of non-precious metal (NPM) electrocatalysts for efficient nitrite-to-ammonia upcycling is key to enabling a sustainable society. Here, an earth-abundant NiFe layered double hydroxide (LDH) is prepared to electrochemically reduce nitrite with a Faradaic efficiency as high as 85 %, an ammonia selectivity reaching 98 %, and an ammonia yield rate up to 351 μmol h−1 mgcat−1, rivaling the performance metrics of state-of-the-art NPM catalysts. NiFe LDH further displays excellent stability after 10 consecutive electrolysis runs with its nanostructure unperturbed. By conducting electroreduction of nitrite in a range of solutions, the electrolyte identity is found to play an important role in dictating the overall nitrite removal activity. Through a comparative study with MgFe and NiAl inorganic solids, Ni and Fe are demonstrated to boost nitrite valorization rate as well as ammonia selectivity and yield in a synergistic manner. Taken together, these low-cost catalysts provide a promising strategy for one-step conversion of nitrite into ammonia exclusively with implications in next-generation wastewater treatment and green industrial commodity production.