Correlating reductive vanadium oxide transformations with electrochemical N2 activation and ammonia formation.
Kabirat Balogun1, Qasim Adesope1, Stella Amagbor1
1Dept. of Chemistry, University of North Texas, Denton, TX, 76203, USA. g.katsoukis@utwente.nl.
Physical Chemistry Chemical Physics : PCCP
|June 10, 2025
Summary
Electrochemical reduction of nitrogen to ammonia (E-NRR) mechanisms were studied using vanadium oxide electrodes. Transient redox transitions, not just static V2O3, are key for nitrogen activation and ammonia synthesis.
Area of Science:
- Electrochemistry
- Materials Science
- Catalysis
Background:
- Electrochemical reduction of nitrogen to ammonia (E-NRR) offers a sustainable alternative to the Haber-Bosch process.
- Understanding the molecular-scale mechanisms of E-NRR is crucial for developing efficient catalysts.
- Vanadium oxides are explored as potential electrocatalysts for E-NRR in neutral aqueous media.
Purpose of the Study:
- To elucidate the reaction mechanisms of E-NRR on vanadium oxide electrodes in neutral electrolyte (pH 7).
- To investigate the role of surface evolution and redox transitions of vanadium species during E-NRR.
- To identify key intermediates and conditions for ammonia formation.
Main Methods:
- In situ electrochemical infrared reflection-absorption spectroscopy (EC-IRRAS) was employed to monitor surface changes.
- Ex situ X-ray photoelectron spectroscopy (XPS) characterized the initial electrode composition.
- Electrochemical measurements were performed in a nitrogen-saturated neutral aqueous electrolyte.
Main Results:
- Vanadium oxide electrodes transformed from V5+ (V2O5) to anionic vanadates and then to V2O4 upon reduction.
- Ammonia formation initiated at -0.28 V vs. RHE, coinciding with a V2O4 to V2O3 phase transition.
- Adsorbed N2 was observed at -0.28 to -0.38 V vs. RHE, indicating an associative E-NRR mechanism.
Conclusions:
- Transient redox transitions (V5+ → V4+ → V3+) are critical for N2 activation in E-NRR.
- Vanadium oxides act as dynamic platforms for E-NRR, with surface evolution playing a key role.
- The findings highlight the potential of vanadium oxides for efficient and environmentally friendly ammonia synthesis.
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