EIS Study on Competitive Adsorption at the TiO₂-Solution Interface

Area of Science:

• Materials Science
• Electrochemistry
• Surface Chemistry

Background:

• Ionic adsorption on electrode surfaces is critical for electrocatalytic reactions and corrosion science.
• Understanding competitive adsorption mechanisms is essential for optimizing electrode performance.

Purpose of the Study:

• To demonstrate the utility of Electrochemical Impedance Spectroscopy (EIS) for identifying competitive ionic adsorption.
• To investigate the adsorption behavior of phosphate and chloride ions on a Ti/TiO2 electrode surface in a complex solution.

Main Methods:

• Utilized EIS to analyze the adsorption of phosphate and chloride ions on a Ti/TiO2 electrode.
• Varied phosphate ion concentration and solution pH (5.0, 7.0, 9.0) in a high chloride background (100 mM).
• Analyzed impedance-concentration curves to identify adsorption species transitions and phosphate adsorption modes.

Main Results:

• Observed a clear transition from chloride-dominated to phosphate-dominated adsorption with increasing phosphate concentration.
• Identified a transformation in phosphate adsorption mode, shifting from bidentate to monodentate at higher concentrations under neutral/alkaline conditions.
• Detected competitive adsorption transitions in impedance-concentration curves up to approximately 5 mM phosphate concentration.

Conclusions:

• EIS is an effective method for detecting competitive adsorption of ions on electrode surfaces.
• The study elucidates the competitive adsorption dynamics between phosphate and chloride ions on Ti/TiO2.
• Provides a valuable approach for precursor adsorption behavior analysis in corrosion science.