Trifunctional Synergistic Trigger in MOF-Derived Mn-Doped Co ₃ O ₄ for Enhanced Nitrate Electroreduction

Electrochemical nitrate reduction reaction (NO 3 RR) to ammonia (NH 3 ) represents a sustainable route for both wastewater purification and value-added chemical product. However, developing industrially viable catalysts that combine high efficiency and robust durability remains a challenge. Here, we engineer a series of Mn-doped Co 3 O 4 catalysts with controlled Mn contents via a metal–organic framework (MOF)-derived approach. A distinct volcano-type relationship is observed between the Mn doping level and the NO 3 RR performance, where optimal Mn 15 –Co 3 O 4 achieves a remarkable nitrate (NO 3 – ) conversion of 95.48%, 99.19% selectivity and 96.71% Faradaic efficiency toward NH 3 . More importantly, we unveil that this activity trend is synchronously mirrored by the evolution of three key descriptors: the electrochemically active surface area, the Co 2+ /Co 3+ ratio, and the concentration of oxygen vacancies, all peaking at the same optimal doping level. This correlation establishes a robust structure–activity relationship, demonstrating that moderate Mn doping maximally synergizes morphological advantages and electronic modulation. This work offers an intriguing pathway for the application of MOF-derived materials and provides valuable insights for the rational design of efficient electrocatalysts.