Oxygen Vacancy Modulation in CuCo₂O₄: Structural Reconstruction-Driven Kinetic Equilibrium for Nitrate Reduction to...

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Electrocatalytic nitrate reduction reaction (NO3RR) is promising for sustainable ammonia synthesis.
• Challenges include precise reaction control due to multiple electron/proton transfers, leading to low Faradaic efficiency (FE) and ammonia (NH3) selectivity.
• Existing catalysts struggle with efficient deoxygenation and hydrogenation steps.

Purpose of the Study:

• To address the limitations in NO3RR for ammonia synthesis.
• To achieve kinetic equilibrium for enhanced NO3RR performance.
• To investigate the structure-performance relationship of CuCo2O4 electrocatalysts with varying oxygen vacancy (OV) levels.

Main Methods:

• Systematic probing of CuCo2O4 reconstruction with gradient OV levels.
• Characterization using Scanning Electron Microscopy (SEM) and in situ Raman spectroscopy.
• Mechanism studies involving dynamic analysis and Density Functional Theory (DFT) calculations.

Main Results:

• CuCo2O4 transformed into a Co(OH)2/CuCo2Ox heterostructure, irrespective of OV levels.
• OV facilitated nitrate adsorption, while reconstructed Co(OH)2 provided active hydrogen (*H).
• Achieved a superior NH3 Faradaic efficiency (FE) of 96.2% at -0.3 V vs reversible hydrogen electrode (RHE).

Conclusions:

• A synergistic strategy combining OV tuning and structural reconstruction enables kinetic equilibrium in NO3RR.
• The dynamic electrocatalyst design offers a new pathway for high-performance ammonia synthesis.
• This approach significantly improves NH3 selectivity and efficiency in electrocatalytic nitrate reduction.