Selective NO^- Electroreduction to Ammonia on Isolated Ru Sites

Area of Science:

• Electrochemistry
• Catalysis
• Environmental Chemistry

Background:

• Nitrate and nitrite are prevalent industrial wastewater and groundwater contaminants.
• Sustainable ammonia production is crucial, with electroreduction of nitrogen oxides offering an alternative to the energy-intensive Haber-Bosch process.
• Developing selective catalysts for nitrate/nitrite electroreduction to ammonia is challenging due to competing reactions like hydrogen evolution and N-N coupling.

Purpose of the Study:

• To design and demonstrate a catalyst for selective electroreduction of nitrate and nitrite to ammonia.
• To investigate the reaction mechanism and identify key steps for optimizing ammonia synthesis.
• To provide a more sustainable pathway for ammonia production.

Main Methods:

• Synthesis and characterization of isolated ruthenium sites as catalysts.
• Electrochemical reduction experiments to evaluate catalytic performance (Faradaic efficiency, potential).
• Density Functional Theory (DFT) calculations to simulate reaction mechanisms and identify rate-limiting steps.

Main Results:

• Isolated ruthenium sites demonstrated high selectivity for nitrate/nitrite electroreduction to ammonia.
• Maximal Faradaic efficiencies of 97.8% for nitrite and 72.8% for nitrate reduction were achieved at -0.6 V and -0.4 V, respectively.
• DFT calculations identified the *NO → *NOH step as the potential rate-limiting step for ammonia formation on single-atom Ru sites.

Conclusions:

• Isolated ruthenium sites are effective catalysts for selective nitrate/nitrite-to-ammonia conversion.
• The findings offer a promising strategy for sustainable ammonia production from nitrogen oxides.
• Understanding the reaction mechanism provides insights for designing advanced electrocatalysts.