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Counterion Distribution in the Stern Layer on Charged Surfaces
Tianyi Han1, Wanxing Xu1, Jie Han1
1State Key Laboratory of Tribology in Advanced Equipment, Tsinghua University, Beijing 100084, People's Republic of China.
We directly measured counterion adsorption density in the Stern layer, finding it depends on surface charge, not bulk concentration. Charge inversion concentration is sensitive to ion type and valence, crucial for understanding interfacial ion behavior.
Area of Science:
- Physical Chemistry
- Surface Science
- Electrochemistry
Background:
- Counterion adsorption at solid-liquid interfaces is critical for many applications.
- Quantifying counterion adsorption density within the Stern layer remains a challenge.
Purpose of the Study:
- To directly determine the counterion adsorption density in the Stern layer.
- To investigate the factors influencing Stern layer adsorption and charge inversion concentration.
Main Methods:
- Extension of the Grahame equation.
- Streaming current measurements on various solid surfaces in aqueous electrolytes.
Main Results:
- Direct determination of surface charge density at the shear plane.
- Counterion adsorption density in the Stern layer correlates with surface charge density, minimally impacted by bulk ion concentration.
- Charge inversion concentration is primarily influenced by ion type and valence, not the charged surface itself.
Conclusions:
- Provides a direct method for evaluating Stern layer counterion adsorption.
- Highlights the roles of ionic competitive adsorption and ion-ion correlations in charge inversion.
- Offers a framework for understanding ion distribution in interfacial processes involving the Stern layer.
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