Grain-resolved mapping of oxygen evolution activation on a Ni-superalloy

Area of Science:

• Materials Science
• Electrochemistry
• Surface Science

Background:

• The oxygen evolution reaction (OER) is crucial for energy conversion technologies.
• Understanding OER activation mechanisms at the nanoscale is essential for catalyst development.
• Nickel-based superalloys show promise as OER electrocatalysts, but their performance is linked to microstructure.

Purpose of the Study:

• To perform the first grain-resolved mapping of OER activation on a Ni-based superalloy.
• To investigate the influence of grain size and orientation on OER performance.
• To establish identical-location electron backscatter diffraction (IL-EBSD) as a tool for microstructure-guided electrocatalyst design.

Main Methods:

• Identical-location electron backscatter diffraction (IL-EBSD) for crystallographic analysis.
• Correlative microscopy techniques including identical-location scanning electron microscopy (IL-SEM) and identical-location energy-dispersive X-ray spectroscopy (IL-EDS).
• Scanning Electrochemical Cell Microscopy (SECCM) for electrochemical activity mapping.

Main Results:

• NiFe (oxy)hydroxide film formation and OER activity are strongly influenced by grain size and orientation.
• (111)-oriented and smaller grains exhibited pronounced structural, chemical, and electrochemical transformations during OER.
• Significant microstructure heterogeneity was observed in OER activation across the superalloy surface.

Conclusions:

• IL-EBSD is a powerful technique for analyzing OER activation at the grain level.
• Microstructure, specifically grain size and orientation, plays a critical role in OER performance of Ni-based superalloys.
• These findings enable the microstructure-guided design of more efficient electrocatalysts for energy applications.