Tuning Active Hydrogen on Reconstructed RuO₂/Co(OH)₂ Catalysts for Selective Ammonia Synthesis

Area of Science:

• Electrochemistry
• Catalysis
• Sustainable Chemistry

Background:

• Electrochemical nitrate reduction (eNO3RR) is key for sustainable ammonia production and nitrogen cycle support.
• Precatalyst reconstruction and complex reaction intermediates hinder eNO3RR efficiency.

Purpose of the Study:

• To improve ammonia production via eNO3RR by managing active hydrogen (*H) generation and precatalyst reconstruction.
• To develop a stable and efficient catalyst for eNO3RR and related applications.

Main Methods:

• Tailoring the RuO2/Co3O4 precatalyst and optimizing electrolyte composition (OH- and NO3- concentration).
• In situ catalyst reconstruction to RuO2/Co(OH)2.
• Electrochemical performance testing and mechanistic studies.

Main Results:

• Achieved an ammonia yield of 35.9 ± 0.9 mg h-1 cm-2 and Faradaic efficiency (FE) of 98.1 ± 2.6% at -0.3 V vs RHE.
• Demonstrated stable operation for over 260 hours in rechargeable Zn-NO3- batteries.
• Identified electron-rich RuO2 facilitating *H generation and subsequent hydrogenation of nitrogenous intermediates on Co(OH)2.

Conclusions:

• Strategic management of *H generation and precatalyst reconstruction is crucial for selective ammonia formation in eNO3RR.
• The RuO2/Co(OH)2 catalyst shows significant potential for ammonia synthesis, wastewater treatment, and energy storage.
• Understanding electron and proton transfer is essential for designing efficient eNO3RR catalytic systems.