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Cation Modifies Interfacial Water Structures on Platinum during Alkaline Hydrogen Electrocatalysis.
Pengtao Xu1, Ruiyu Wang2,3, Haojian Zhang1
1Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14850, United States.
Cations like potassium (K+), lithium (Li+), and barium (Ba2+) influence electrocatalysis by altering interfacial water structure. This cation hydration-mediated mechanism impacts sustainable fuel production.
Area of Science:
- Surface Science
- Electrochemistry
- Computational Chemistry
Background:
- Electrocatalytic interfaces are crucial for sustainable fuel and chemical synthesis.
- Cation-dependent activity is observed in many reactions, but the underlying mechanisms remain unclear.
Purpose of the Study:
- To investigate the effect of different cations (K+, Li+, Ba2+) on interfacial water structure at the platinum (Pt) electrode.
- To elucidate the role of interfacial water structure in cation-mediated electrocatalysis.
Main Methods:
- Second-harmonic generation (SHG) spectroscopy to probe interfacial water orientation.
- Classical molecular dynamics (MD) simulations to model cation-water interactions and interfacial structure.
Main Results:
- SHG experiments and MD simulations revealed that cations alter the orientation of interfacial water molecules on Pt.
- Ba2+ resulted in smaller optical susceptibilities (χH(2) and χH(3)) compared to K+, indicating a more disordered water structure.
- MD simulations showed that cation hydration competes with water alignment, governing the net water orientation.
Conclusions:
- The study supports a cation hydration-mediated mechanism for hydrogen electrocatalysis, involving water dissociation and cation-assisted exchange.
- Interfacial water structure significantly influences electrocatalytic performance, even with seemingly inert additives like cations.
- Understanding cation effects on interfacial water is key to optimizing electrocatalytic processes for sustainable energy applications.
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