Structural Evolution of Metal (Oxy)hydroxide Nanosheets during the Oxygen Evolution Reaction

Area of Science:

• Electrochemistry and Materials Science
• Nanomaterials for Catalysis

Background:

• Metal (oxy)hydroxides (MO_xH_y) are highly active electrocatalysts for the oxygen evolution reaction (OER) in alkaline media.
• Understanding the nanostructure and its dynamic evolution under electrochemical conditions is crucial for optimizing OER catalyst performance.
• Existing research has characterized activity and overpotentials but lacks in-depth analysis of nanoscale structural changes.

Purpose of the Study:

• To investigate the structural evolution of Ni_1-δCo_δO_xH_y nanosheets with varying Ni:Co ratios during electrochemical cycling.
• To understand the influence of composition on the nanostructure and stability of these OER catalysts.
• To correlate nanostructural dynamics with catalytic performance and material integrity.

Main Methods:

• Synthesis of Ni_1-δCo_δO_xH_y nanosheets with controlled Ni:Co ratios.
• In operando atomic force microscopy (AFM) to monitor structural changes during electrochemical cycling.
• Analysis of nanosheet porosity, roughness, and overall structural integrity.

Main Results:

• Cobalt addition to NiO_xH_y nanosheets increases porosity, reducing mechanical stress and enhancing stability during redox cycling.
• Ni_1-δCo_δO_xH_y nanosheets with high cobalt content resist the restructuring observed in pure NiO_xH_y, which forms nanoparticle assemblies.
• Ni_0.8Fe_0.2O_xH_y nanosheets exhibit increased roughness during cycling while maintaining structural integrity.

Conclusions:

• The nanostructure and composition of metal (oxy)hydroxides significantly influence their structural dynamics and stability under electrochemical conditions.
• Incorporating cobalt into NiO_xH_y is a promising strategy to improve catalyst durability for the oxygen evolution reaction.
• These findings provide fundamental insights for designing robust and efficient OER electrocatalysts.