Turning waste to treasure: Hierarchical Ni–Cu borate layered double hydroxide@Ni foam as durable electrocatalyst for ammonia electrooxidation reaction

Developing efficient and selective electrocatalysts for electrochemical ammonia oxidation (eAOR), coupled with proper electrochemical processes, offers promising opportunities for recycling ammonia into valuable fertilizers and as a potential technology for energy production and storage applications. Here, we introduce Ni(OH) 2 /Ni x Cu y B@NF electrodes, developed by in-situ solvothermal methods, as highly effective and durable electrocatalytic materials. The eAOR features of Ni(OH) 2 /Ni x Cu y B@NF displays the smallest overpotential of 130 mV (at 50 mA cm −2 ) and attained a enhanced current response of 178.3 mA cm −2 (@ 1.60 V RHE ). As shown by the electrocatalytic features and stability of Ni(OH) 2 /Ni x Cu y B@NF films at 1.43 V for an eAOR of 50 mA cm −2 , the HER current was 100 mA cm −2 at 99 mV, the smallest value among all Ni-based electrocatalysts studied. Gas chromatography (GC) experiments show that ammonia produces N 2 in the electrochemical cell at different times. In the eAOR-HER system, impressive electrocatalytic performance has been observed with higher FE of N 2 and H 2 was 47 % and 27.1 %. A two-electrode arrangement of Ni(OH) 2 /Ni x Cu y B@NF needs only 1.53 V to split ammonia to acquire 10 mA cm −2 , which is lower than any other electrode material. Based on the results, Ni(OH) 2 /Ni x Cu y B@NF might be a suitable system for wastewaters bearing high levels of ammonia, generating more sustainable hydrogen from wastewater, and recycling fertilizers.