Controlling the Double Layer of Platinum by Selective Passivation of Step Sites Using Adatom Modification

Area of Science:

• Electrochemistry
• Surface Science
• Materials Science

Background:

• The electric double layer structure at platinum electrodes is not fully understood, deviating from established theories.
• Stepped platinum surfaces exhibit complex adsorption behavior, unlike flat Pt(111), complicating capacitance measurements.
• Previous work highlighted potential-independent hydroxyl adsorption on (110)-steps and potential-dependent adsorption on (100)-steps.

Purpose of the Study:

• To investigate the impact of adatom modification on the electric double layer structure at stepped platinum surfaces.
• To elucidate the role of platinum step-site chemistry in determining electrochemical and electrocatalytic properties.
• To demonstrate controllable tuning of platinum surface properties via selective adatom deposition.

Main Methods:

• Selective passivation of platinum step sites using gold (Au*) and silver (Ag*) adatoms.
• Electrochemical capacitance measurements on modified stepped platinum surfaces.
• Assessment of electrocatalytic activity, specifically CO oxidation, on modified surfaces.

Main Results:

• Au* adatom modification suppressed step-specific adsorption on (100)-type stepped Pt surfaces, restoring electrostatic behavior and reversing capacitance trends.
• Ag* adatom modification introduced a chemical contribution, significantly increasing capacitance and enhancing CO oxidation activity.
• Adsorption of oxophilic species on Ag* was responsible for the observed enhancement in CO oxidation.

Conclusions:

• Platinum step-site chemistry significantly influences the electric double-layer structure and electrocatalytic activity.
• Selective adatom modification provides a powerful method to tune and probe these surface properties with high controllability.
• This approach offers new avenues for designing advanced platinum-based electrocatalysts.