Double Layer of a Gold Electrode Probed by AFM Force Measurements

Area of Science:

• Surface Science
• Electrochemistry
• Colloid Science

Background:

• Understanding the gold/electrolyte interface is crucial for applications in electrocatalysis and sensing.
• Electric double layer (EDL) interactions govern interfacial phenomena.
• Gold electrodes exhibit complex behavior influenced by solution chemistry and applied potential.

Purpose of the Study:

• To quantify EDL interactions between a gold electrode and a silica probe using colloidal probe atomic force microscopy.
• To investigate the influence of pH, salt concentration, and applied potential on the gold/solution interface.
• To characterize the amphifunctional nature of the gold/electrolyte interface.

Main Methods:

• Colloidal probe atomic force microscopy (CP-AFM) to measure forces.
• Fitting force-distance curves using Derjaguin-Landau-Verwey-Overbeek (DLVO) theory.
• Systematic variation of electrolyte pH, salt concentration, and applied electric potential.

Main Results:

• The gold electrode behaves as both a reversible and polarizable interface.
• Gold surface potential is dependent on solution pH and applied external potential.
• A linear relationship was observed between the double layer potential and the applied potential.

Conclusions:

• The gold/electrolyte interface can be effectively modeled using an amphifunctional double layer model.
• Proton adsorption/desorption on oxidic groups explains the pH dependence.
• Results provide a foundation for interpreting adsorption studies on gold surfaces.