pKa as a Predictive Descriptor for Electrochemical Anion Adsorption.
Mohammad H Hasan1, Ian T McCrum1
1Department of Chemical and Biomolecular Engineering, Clarkson University, 8 Clarkson Ave., Potsdam, NY 13699.
Angewandte Chemie (International Ed. in English)
|February 10, 2024
Summary
Anion adsorption strength on platinum surfaces correlates with acidity and electron affinity. Understanding these factors is key for designing better catalysts and improving wastewater treatment processes.
Area of Science:
- Surface chemistry
- Electrocatalysis
- Materials science
Background:
- Anion adsorption on metal surfaces is crucial for catalysis and environmental remediation.
- Anions can act as reactive intermediates or blocking species in electrocatalysis, influencing reaction rates.
- Understanding adsorption strength is key to optimizing these applications.
Purpose of the Study:
- To measure the adsorption energy of carboxylic acids on a platinum (111) surface.
- To identify key molecular descriptors governing anion adsorption strength.
- To provide insights for designing improved catalysts and treatment methods.
Main Methods:
- Experimental measurement of adsorption energies of carboxylic acids on Pt (111) in aqueous solution.
- Density functional theory (DFT) modeling to decompose adsorption energy.
- Correlation analysis between adsorption strength, pKa, and electron affinity.
Main Results:
- Adsorption strength of carboxylate anions linearly correlates with their acid-dissociation constant (pKa).
- DFT analysis revealed that electron affinity of the neutral radical is the primary determinant of anion adsorption strength.
- Carboxyl radical adsorption energies were similar, highlighting the role of electron removal energy.
Conclusions:
- Both acidity (pKa) and electron affinity are predictive descriptors for anion adsorption strength on platinum surfaces.
- This finding is particularly relevant for anions with similar structures and surface binding atoms.
- The results offer a pathway for rational design in catalysis and surface modification.
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