Boosting electrochemical nitrate-to-ammonia conversion by self-supported MnCo₂O₄ nanowire array

Area of Science:

• Electrochemistry
• Materials Science
• Environmental Chemistry

Background:

• Electrocatalytic reduction of nitrate (NO3-) offers a sustainable pathway for ammonia (NH3) synthesis and pollutant removal.
• Current challenges include the need for highly efficient and stable catalysts to overcome low selectivity and activity.

Purpose of the Study:

• To develop a self-supported spinel-type MnCo2O4 nanowire array catalyst.
• To investigate its efficacy in the direct electrocatalytic reduction of nitrate to ammonia.
• To understand the catalytic mechanism at the atomic level.

Main Methods:

• Synthesis of a self-supported spinel-type MnCo2O4 nanowire array.
• Electrocatalytic performance testing for nitrate reduction.
• Density functional theory (DFT) calculations to analyze reaction pathways and energy barriers.

Main Results:

• The MnCo2O4 nanowire array exclusively catalyzed nitrate to ammonia conversion.
• Achieved a high Faradic efficiency of 97.1% for NH3 production.
• Demonstrated a high NH3 yield rate of 0.67 mmol h-1 cm-2.
• DFT analysis indicated a low energy barrier (0.46 eV) for the *NO to *NOH step on the MnCo2O4 (220) surface.

Conclusions:

• The developed MnCo2O4 nanowire array is a highly efficient and selective electrocatalyst for nitrate reduction to ammonia.
• This catalyst presents a promising solution for simultaneous environmental remediation and ammonia synthesis.
• The findings provide insights into catalyst design for efficient nitrogen electrocatalysis.