Design of the Low-Loading NiFe Hydroxide Alkaline Oxygen Evolution Catalyst Layers Based on Inverse Opal Supports

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Anion exchange membrane water electrolyzers offer high efficiency and low cost.
• Nickel-iron layered double hydroxides (NiFe LDH) are active oxygen evolution reaction (OER) catalysts but suffer from low conductivity and limited active site accessibility.
• High-surface-area inverse-opal (IO) metallic supports can enhance NiFe LDH performance.

Purpose of the Study:

• To investigate the impact of void size and metal type (Ni, Fe, Co) of IO supports on NiFe LDH catalyst performance for OER.
• To develop highly active and stable NiFe LDH/IO catalyst layers for water electrolysis.

Main Methods:

• Fabrication of NiFe LDH coatings on inverse-opal (IO) metallic supports (Ni, Fe, Co) with varying void sizes.
• Electrochemical characterization of catalyst layers to evaluate OER activity and stability.
• Optimization of NiFe LDH coating thickness and IO void size.

Main Results:

• The optimized NiFe LDH/Ni IO composite (900 nm thickness, 320 ± 10 nm void size) achieved a high OER rate of 100 mA cm_geom.^-2 at an overpotential of 0.307 V.
• The catalyst demonstrated a mass-normalized activity of 1000 A g_{NiFe bspLDH}^-1.
• Stable operation at 100 mA cm_geom.^-2 was maintained for at least 120 hours.

Conclusions:

• Inverse-opal metallic supports significantly improve the performance of NiFe LDH OER catalysts by increasing surface area and conductivity.
• Optimized NiFe LDH/Ni IO catalysts show great promise for efficient and durable anion exchange membrane water electrolyzers.
• This approach effectively addresses the limitations of NiFe LDH, paving the way for cost-effective hydrogen production.