Deciphering and Suppressing Over‐Oxidized Nitrogen in Nickel‐Catalyzed Urea Electrolysis
Jianan Li, Jili Li, Tao Liu, Lin Chen, Yefei Li, Hualin Wang, Xiurong Chen, Ming Gong, Zhi‐Pan Liu, Xuejing Yang
Abstract
Abstract Urea electrolysis is a prospective technology for simultaneous H 2 production and nitrogen suppression in the process of water being used for energy production. Its sustainability is currently founded on innocuous N 2 products; however, we discovered that prevalent nickel‐based catalysts could generally over‐oxidize urea into NO 2 − products with ≈80 % Faradaic efficiencies, posing potential secondary hazards to the environment. Trace amounts of over‐oxidized NO 3 − and N 2 O were also detected. Using 15 N isotopes and urea analogues, we derived a nitrogen‐fate network involving a NO 2 − ‐formation pathway via OH − ‐assisted C−N cleavage and two N 2 ‐formation pathways via intra‐ and intermolecular coupling. DFT calculations confirmed that C−N cleavage is energetically more favorable. Inspired by the mechanism, a polyaniline‐coating strategy was developed to locally enrich urea for increasing N 2 production by a factor of two. These findings provide complementary insights into the nitrogen fate in water–energy nexus systems.