Boosting active hydrogen generation by anchored Ru sites in Co3O4 for nitrate-to-ammonia electrosynthesis

The electrochemical reduction of nitrate to ammonia can serve as an effective complement to the traditional Haber-Bosch process. Currently, rapid and continuous ammonia production is challenging because of the multistep hydrogenation process and the constant alkalinization of the electrolyte. Herein, Ru atoms are incorporated into the octahedral sites of Co3O4 to achieve an ammonia yield rate of 24.6 mg h-1 cm-2. Electrochemical in situ spectroscopic analyses and theoretical calculations reveal that Ru sites improve water molecule coverage and facilitate the production of active hydrogen atoms, leading to stable and orderly ammonia production. Furthermore, a peak power density of 32.28 mW cm-2, a high ammonia Faradaic efficiency of 98.2%, and excellent durability (91 h) are achieved in a Ru-Co3O4-based Zn-nitrate battery, indicating its practical applicability. This work may provide a method for efficient nitrate reduction to ammonia or other hydrogenation reactions via the synergistic modulation of active sites.