Efficient Electrochemical NO Reduction at Low Overpotential via Synergistic RuCu Alloy Nanoparticles

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Electrochemical nitric oxide reduction (NORR) is a potential alternative to the energy-intensive Haber-Bosch process for ammonia synthesis.
• Current NORR catalysts, often transition metals, face challenges like side reactions, mass transfer limitations, and high overpotentials due to intermediate overbinding.
• Noble metals offer fast electron transfer but poor NO adsorption, while transition metals have tunable adsorption but suffer from overbinding.

Purpose of the Study:

• To develop a novel catalytic strategy for efficient and selective ammonia synthesis via NORR.
• To overcome the limitations of traditional transition metal catalysts by employing a noble-metal alloying approach.
• To investigate the synergistic effects of alloying ruthenium (Ru) and copper (Cu) for enhanced NORR performance.

Main Methods:

• Synthesis of Ru-Cu alloy nanoparticles supported on nitrogen-doped carbon nanorods (Ru_xCu_100-x@NCNR).
• Electrochemical characterization of catalysts, including ammonia yield and Faradaic efficiency measurements at low overpotentials.
• Long-term stability testing and integration into a Zn-NO battery system.
• Mechanistic studies to understand the role of Ru content in modulating NO adsorption and protonation.

Main Results:

• The optimized Ru₅Cu₉₅@NCNR catalyst achieved a high ammonia yield of 32.66 ± 4.38 μmol cm^-2 h^-1 and a Faradaic efficiency of 94 ± 1.25% (FE_NH3) at -0.2 V vs RHE.
• The catalyst demonstrated significantly lower overpotential compared to conventional NORR catalysts, indicating energy-efficient ammonia production.
• Sustained catalytic performance was confirmed through long-term stability tests.
• Successful integration into a Zn-NO battery system validated its practical applicability.

Conclusions:

• Noble-metal alloying, specifically Ru-Cu, synergistically enhances catalytic activity for selective ammonia production via NORR.
• Precise control of Ru content in RuCu alloys is crucial for optimizing NO adsorption and protonation, leading to high NH₃ selectivity.
• The developed Ru_xCu_100-x@NCNR catalyst represents a promising, energy-efficient solution for ammonia synthesis and next-generation energy conversion devices.