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

Area of Science:

• Surface Science
• Electrochemistry
• Materials Science

Background:

• The electric double layer structure at platinum (Pt) electrodes, particularly Pt(111)/HClO4, deviates from established theories.
• Stepped Pt surfaces complicate double-layer studies due to adsorption of hydrogen and hydroxyl species at step sites.
• Previous work showed potential-independent hydroxyl adsorption on (110)-steps and potential-dependent adsorption on (100)-steps.

Purpose of the Study:

• To investigate the effect of selective adatom modification (Au, Ag) on Pt step sites.
• To understand how adatom modification influences electric double-layer structure and capacitance on stepped Pt surfaces.
• To explore the impact of modified step sites on electrocatalytic activity, specifically CO oxidation.

Main Methods:

• Selective passivation of Pt step sites using gold (Au) and silver (Ag) adatoms.
• Measurement of electric double-layer capacitance on modified stepped Pt surfaces.
• Electrocatalytic activity assessment, focusing on CO oxidation.

Main Results:

• Au adatom modification on Pt step sites suppressed specific adsorption, restoring electrostatic behavior to (100)-type stepped surfaces and reversing capacitance trends.
• Ag adatom modification introduced a chemical contribution, significantly increasing capacitance and enhancing CO oxidation activity.
• These findings highlight the controllable tuning of Pt step-site chemistry via adatom deposition.

Conclusions:

• Pt step-site chemistry is highly tunable through selective adatom modification.
• Adatom modification provides a method to probe and control electric double-layer structure and electrocatalytic properties.
• This approach offers significant controllability over interfacial phenomena at electrode surfaces.