Grain Boundaries Boost Oxygen Evolution Reaction in NiFe Electrocatalysts

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Grain boundaries (GBs) in polycrystalline materials are known active sites for some catalytic reactions.
• Evidence for GBs enhancing oxygen evolution reaction (OER) activity in electrocatalysts is limited.
• Understanding GBs' role is crucial for developing efficient electrocatalysts.

Purpose of the Study:

• To investigate the direct effect of grain boundary density on the oxygen evolution reaction (OER) activity of NiFe electrocatalysts.
• To elucidate the mechanism by which GBs influence OER.
• To demonstrate the applicability of GB engineering for polycrystalline electrocatalysts.

Main Methods:

• Combination of electrochemical measurements and chemical analysis.
• In situ electrochemical microscopy to observe OER at GBs.
• High-resolution transmission electron microscopy (HRTEM) to analyze GB structure.

Main Results:

• Grain boundary density directly correlates with the overall OER performance of NiFe electrocatalysts.
• In situ observations confirm OER predominantly occurs at GBs.
• High-index planes exposed at GBs and work function differences contribute to enhanced OER activity.

Conclusions:

• Grain boundaries serve as crucial active sites for oxygen evolution reaction (OER) in NiFe electrocatalysts.
• The study provides direct evidence and mechanistic insights into GB-enhanced OER.
• Engineering grain boundaries is a viable strategy for improving polycrystalline electrocatalyst performance.