Crystal Field Stabilization Energy Asymmetrically Constructed Built-in Electric Fields for Efficient Water Cracking

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Bifunctional electrocatalysts are essential for efficient water electrolysis, enabling both hydrogen and oxygen evolution reactions (HER and OER).
• Achieving simultaneous HER and OER is challenging due to differing intermediate binding affinities.
• Multi-component heterostructures offer a promising approach, but their precise mechanisms require further elucidation.

Purpose of the Study:

• To develop a novel heterogeneous catalyst (NiS/Ni2P@NF) with a built-in electric field (BEF) for enhanced bifunctional water splitting.
• To investigate the role of asymmetrical crystal field stabilization energy (CFSE) in creating the BEF and its impact on catalytic activity.
• To elucidate the division of labor and reaction mechanisms of NiS and Ni2P components in the heterostructure.

Main Methods:

• Synthesis of a heterogeneous catalyst (NiS/Ni2P@NF) leveraging asymmetrical CFSE between NiS and Ni2P.
• Density Functional Theory (DFT) calculations to confirm the BEF and its effect on electron flow and reaction pathways.
• Electrochemical characterization, including control experiments, to evaluate HER and OER performance.

Main Results:

• The constructed NiS/Ni2P@NF catalyst exhibits a built-in electric field (BEF) due to asymmetrical CFSE.
• DFT calculations confirmed that BEF optimizes OER/HER pathways via directional electron movement.
• NiS and Ni2P function as specific active sites for OER and HER, respectively.
• The NiS/Ni2P@NF electrode achieved a low cell voltage of 1.62 V at 10 mA cm⁻² in a H-type electrolyzer for overall water splitting.

Conclusions:

• The strategy of constructing BEF based on asymmetrical CFSE is effective for designing advanced bifunctional electrocatalysts.
• The NiS/Ni2P@NF catalyst demonstrates high efficiency and stability for water electrolysis.
• This approach provides a pathway for precisely controlling local electron flow and designing multifunctional catalysts with distinct compositional functions.