Facet-Dependent Surface Restructuring on Nickel (Oxy)hydroxides: A Self-Activation Process for Enhanced Oxygen...

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Understanding catalyst surface dynamics is crucial for optimizing reaction mechanisms and performance.
• The oxygen evolution reaction (OER) is a key process in energy conversion technologies.
• Nickel-based (oxy)hydroxides are promising OER catalysts.

Purpose of the Study:

• To investigate the facet-dependent surface restructuring of β-Ni(OH)₂ catalysts during OER.
• To elucidate the mechanistic pathway of this restructuring and its impact on catalytic activity.

Main Methods:

• Correlative ex situ and operando characterization techniques.
• Operando liquid transmission electron microscopy (TEM).
• Operando Raman spectroscopy.

Main Results:

• β-Ni(OH)₂ undergoes facet-dependent restructuring at edge sites to form nanoporous, Ni-deficient Ni_1-xO containing Ni³⁺.
• The intermediate β-NiOOH phase plays an active role in both OER catalysis and Ni_1-xO formation.
• Surface restructuring leads to a ~16-fold enhancement in OER activity by increasing active sites and optimizing intermediate bonding.

Conclusions:

• A complete surface restructuring pathway for β-Ni(OH)₂ during OER is identified.
• This self-activation process significantly enhances catalytic performance, with specially prepared catalysts showing a 470-fold improvement over IrO₂.
• Facet engineering and understanding restructuring offer a promising strategy for optimizing metal-(oxy)hydroxide catalysts.