Ru‐Induced Defect Engineering in Co₃O₄ Lattice for High Performance Electrochemical Reduction of Nitrate to Ammonium

AbstractAmidst these growing sustainability concerns, producing NH4+ via electrochemical NO3− reduction reaction (NO3RR) emerges as a promising alternative to the conventional Haber‐Bosch process. In a pioneering approach, this study introduces Ru incorporation into Co3O4 lattices at the nanoscale and further couples it with electroreduction conditioning (ERC) treatment as a strategy to enhance metal oxide reducibility and induce oxygen vacancies, advancing NH4+ production from NO3RR. Here, supported by a suite of ex situ and in situ characterization measurements, the findings reveal that Ru enrichment promotes Co species reduction and oxygen vacancy formation. Further, as evidenced by the theoretical calculations, Ru integration lowers the energy barrier for oxygen vacancy formation, thereby facilitating a more energy‐efficient NO3RR‐to‐NH4+ pathway. Optimal catalytic activity is realized with a Ru loading of 10 at.% (named 10Ru/Co3O4), achieving a high NH4+ production rate (98 nmol s−1 cm−2), selectivity (97.5%) and current density (≈100 mA cm−2) at −1.0 V vs RHE. The findings not only provide insights into defect engineering via the incorporation of secondary sites but also lay the groundwork for innovative catalyst design aimed at improving NH4+ yield from NO3RR. This research contributes to the ongoing efforts to develop sustainable electrochemical processes for nitrogen cycle management.