Dual-Site Catalysis in Ni-Fe Phosphides: Understanding the Bifunctional Mechanism for Water Splitting

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Nickel-iron phosphides are promising bifunctional catalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER).
• Challenges include thermodynamic instability and poorly understood reaction mechanisms at active sites.

Purpose of the Study:

• To synthesize highly exposed Ni2P-Fe2P heterostructures for efficient and stable bifunctional HER and OER.
• To elucidate the underlying mechanisms contributing to enhanced catalytic activity and stability.

Main Methods:

• Synthesis of Ni2P-Fe2P heterostructures.
• Electrochemical characterization to evaluate HER and OER performance.
• Systematic analyses to understand surface stability and reaction kinetics.

Main Results:

• Achieved low and stable overpotentials: 86 mV for HER and 140 mV for OER at 10 mA cm-2.
• Demonstrated remarkable stability at 100 mA cm-2 with overpotentials of 157 mV (HER) and 251 mV (OER).
• Identified self-adaptive surface hydrogenation/oxidation and synergistic effects between Ni2P and Fe2P as key mechanisms.

Conclusions:

• The Ni2P-Fe2P heterostructures exhibit superior bifunctional catalytic activity and stability.
• Understanding the surface mechanisms and interfacial cooperation is crucial for designing advanced phosphide catalysts.
• This work provides a pathway for developing stable and efficient electrocatalysts for energy conversion.