Electrical Double Layer Effects on Alkaline Hydrogen Reactions on Platinum
Sibo Wang1, Chengzhang Wan1,2, Aamir Hassan Shah1
1Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, United States.
Precision Chemistry
|October 31, 2025
Summary
Alkali metal cations and hydroxide anions significantly impact platinum-catalyzed hydrogen reactions in alkaline solutions. Optimizing electrolyte concentrations is key to enhancing electrical double-layer thickness and reaction rates for efficient electrocatalysis.
Area of Science:
- Electrochemistry
- Surface Science
- Catalysis
Background:
- Alkali metal cations (AM+) and hydroxide anions (OH-) play a crucial role in platinum-catalyzed hydrogen evolution and oxidation reactions (HER/HOR) in alkaline media.
- The precise influence of these ions on reaction kinetics remains a subject of debate, necessitating systematic investigation.
Purpose of the Study:
- To systematically investigate the effects of independently varied sodium cation (Na+) and hydroxide anion (OH-) concentrations on HER/HOR rates.
- To elucidate the correlation between electrical double-layer (EDL) thickness, interfacial electric fields, and HER/HOR kinetics.
Main Methods:
- Utilized twenty-eight electrolytes with independently controlled Na+ and OH- concentrations (0.001 to 1.0 M).
- Analyzed the impact of varying ionic concentrations on EDL thickness and surface charge density on platinum electrodes.
- Correlated EDL parameters with measured HER/HOR reaction rates.
Main Results:
- Increasing OH- concentration positively shifts the potential of zero free charge, reducing EDL thickness and enhancing HER/HOR rates by strengthening interfacial electric fields.
- At fixed pH, increasing Na+ concentration initially enhances HER/HOR activity by reducing EDL thickness, but concentrations above 0.1 M paradoxically increase EDL thickness and suppress rates due to ion pairing.
- At pH 14, strong interfacial fields induce partial dehydration, adversely affecting water structure and suppressing HER/HOR activity despite reduced EDL thickness.
Conclusions:
- EDL thickness and interfacial electric fields are critical factors modulating HER/HOR kinetics in alkaline electrolytes.
- Understanding ion-specific effects on EDL structure and water organization is vital for designing efficient platinum-based electrocatalysts.
- This research provides fundamental insights for optimizing alkaline electrolytes for advanced electrochemical energy systems.
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