Surface Structure and Grain Boundary Effects on the Oxygen Evolution Reaction at Gold Electrodes

Area of Science:

• Electrochemistry
• Materials Science
• Surface Science

Background:

• Electrocatalyst surface structure is critical for activity.
• Gold is a model electro-oxidation catalyst, but its oxygen evolution reaction (OER) behavior near its oxidation potential is understudied.
• Understanding structure-activity relationships is key to designing efficient electrocatalysts.

Purpose of the Study:

• To correlate the crystallographic structure of polycrystalline gold with its electrocatalytic behavior for the OER.
• To investigate gold oxidation and OER activity at grain boundaries.
• To elucidate the role of grain structure and boundaries in electrocatalysis.

Main Methods:

• Combining voltammetric scanning electrochemical cell microscopy (SECCM) for high spatial resolution electrochemical mapping.
• Utilizing electron backscatter diffraction (EBSD) for crystallographic orientation analysis.
• Recording potential-dependent electrochemical movies to visualize dynamic processes.

Main Results:

• Gold oxidation and reduction exhibit clear grain-dependent behavior.
• The oxygen evolution reaction (OER) shows less dependence on individual grain orientation.
• Distinct grain boundaries display either enhanced or suppressed OER activity, correlated with electrochemical active surface area, roughness, and dislocation density.
• SECCM successfully mapped electrochemical activity at grain boundaries.

Conclusions:

• Gold's OER activity is influenced by grain boundaries more than individual grain orientation.
• Grain boundaries play a significant role in electrocatalysis, affecting activity through factors like surface area and defects.
• SECCM is a powerful tool for mapping electrocatalytic activity at underexplored regions like grain boundaries.