Phase Locking of NiOOH@β-Ni(Fe)OOH Reconstructed Simultaneously for Robust Oxygen Evolution at High Current Density.

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• NiFe layered double hydroxides (LDH) reconstruct to β-Ni(Fe)OOH during oxygen evolution, which can overcharge to inactive γ-Ni(Fe)OOH.
• High-potential and high-current density conditions accelerate this detrimental overcharging, reducing electrocatalyst performance.

Purpose of the Study:

• To develop a strategy for maintaining the activity and stability of NiFe-based electrocatalysts under demanding conditions.
• To investigate the mechanism of phase stabilization in reconstructed heterogeneous materials.

Main Methods:

• Simultaneous reconstruction of NiMoO4@NiFe LDH into NiOOH@β-Ni(Fe)OOH.
• Electrochemical testing including overpotential measurements and stability tests in anion exchange membrane water electrolyzers (AEMWE).
• In situ Raman spectroscopy and density functional theory (DFT) calculations.

Main Results:

• The NiOOH@β-Ni(Fe)OOH catalyst achieved an ultralow overpotential of 203 mV at 10 mA cm⁻² and 1 A cm⁻² at 1.81 V in AEMWE.
• Demonstrated significantly enhanced stability with a degradation rate of 1.86 mV h⁻¹ at 1 A cm⁻², over 9.5 times lower than γ-Ni(Fe)OOH.
• In situ and DFT studies revealed that the heterogeneous interface suppresses overcharging via interfacial electron donation.

Conclusions:

• Simultaneous reconstruction creates a stable NiOOH@β-Ni(Fe)OOH phase, effectively preventing overcharging into the inactive γ-Ni(Fe)OOH.
• The heterogeneous interface plays a crucial role in phase locking and enhancing electrocatalyst stability.
• This approach offers a promising pathway for developing efficient and durable electrocatalysts for water splitting.