Constructing built-in electric fields via interface engineering in (oxy)phosphides to boost electroreduction nitrate...

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Electrocatalytic nitrate reduction (eNO3RR) is a promising, low-carbon ammonia synthesis method.
• Challenges include low ammonia yield and poor stability due to sluggish hydrogen transfer and unstable active sites at high current densities.

Purpose of the Study:

• To design and synthesize a novel crystalline-amorphous CoNiFe oxides@phosphides (MO@MP) core-shell hybrid catalyst.
• To enhance ammonia yield, Faradaic efficiency, and long-term stability in eNO3RR.

Main Methods:

• In situ electrochemical reconstruction of a CoNiFe phosphide precursor to form MO@MP catalyst.
• Experimental characterizations (e.g., XRD, TEM, XPS) and density functional theory (DFT) calculations.
• Electrochemical testing for ammonia synthesis and stability under industrial current densities.

Main Results:

• The MO@MP catalyst exhibits synergistic effects between Fe3O4 and Co/Ni(OH)2 phases for nitrate adsorption and water dissociation.
• The core-shell structure facilitates hydrogen transfer and suppresses the hydrogen evolution reaction (HER).
• Optimized MO@MP-2 achieved 3.69 mmol cm-2 h-1 ammonia yield and 99% Faradaic efficiency at -0.5 V, with >100 h stability.

Conclusions:

• The MO@MP catalyst demonstrates exceptional activity and stability for eNO3RR.
• The crystalline-amorphous core-shell architecture and interface engineering are effective strategies for catalyst design.
• This approach offers a universal strategy for advanced catalyst development in ammonia electrosynthesis.