Deciphering Iron-Dependent Activity in Oxygen Evolution Catalyzed by Nickel-Iron Layered Double Hydroxide

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Nickel iron oxyhydroxide is a benchmark catalyst for the oxygen evolution reaction (OER) in alkaline media.
• The precise role of iron ions in enhancing OER activity remains under investigation.

Purpose of the Study:

• To elucidate the function of iron sites in nickel iron layered double hydroxides (LDHs) during OER.
• To establish a correlation between iron content, structural disorder, and catalytic activity.

Main Methods:

• Utilized oxygen isotope labeling and operando Raman spectroscopy.
• Investigated a series of structurally defined Ni and NiFe LDHs.
• Quantified turnover frequencies (TOFs) for both Ni and Fe sites.

Main Results:

• Fe sites exhibit 20-200 times higher TOFs than Ni sites, dominating catalysis at ≥4.7% Fe content.
• Increased Fe content leads to greater structural disorder in the NiOOH host.
• A volcano-type correlation was observed between Fe site TOFs and NiOOH structural disorder.

Conclusions:

• Iron sites are the primary active centers for OER in NiFe LDHs.
• Structural disorder of the NiOOH host significantly influences catalytic activity.
• Strategies focusing on structural ordering can improve OER catalyst performance.