Explanation of Dramatic pH-Dependence of Hydrogen Binding on Noble Metal Electrode: Greatly Weakened Water Adsorption at High pH
Abstract
Hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER) are both 2 orders slower in alkaline electrolyte than in acidic electrolyte, but no explanation has been provided. The first step toward understanding this dramatic pH-dependent HOR/HER performance is to explain the pH-dependent hydrogen binding to the electrode, a perplexing behavior observed experimentally. In this work, we carried out Quantum Mechanics Molecular Dynamics (QMMD) with explicit considerations of solvent and applied voltage ( U) to in situ simulate water/Pt(100) interface in the condition of under-potential adsorption of hydrogen ( H UPD). We found that as U is made more negative, the electrode tends to repel water, which in turn increases the hydrogen binding. We predicted a 0.13 eV increase in hydrogen binding from pH = 0.2 to pH = 12.8 with a slope of 10 meV/pH, which is close to the experimental observation of 8 to 12 meV/pH. Thus, we conclude that the changes in water adsorption are the major causes of pH-dependent hydrogen binding on a noble metal. Furthermore, the new insight of critical role of surface water in modifying electrochemical reactions provides a guideline in designing HER/HOR catalyst targeting for the alkaline electrolyte.
- Authors:
-
[1];
[1];
[1]
- California Inst. of Technology (CalTech), Pasadena, CA (United States)
- California Inst. of Technology (CalTech), Pasadena, CA (United States); Soochow Univ., Jiangsu (China)
- Publication Date:
- Research Org.:
- California Inst. of Technology (CalTech), Pasadena, CA (United States)
- Sponsoring Org.:
- USDOE Office of Science (SC)
- OSTI Identifier:
- 1467598
- Grant/Contract Number:
- SC0004993
- Resource Type:
- Accepted Manuscript
- Journal Name:
- Journal of the American Chemical Society
- Additional Journal Information:
- Journal Volume: 140; Journal Issue: 25; Journal ID: ISSN 0002-7863
- Publisher:
- American Chemical Society (ACS)
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Citation Formats
Cheng, Tao, Wang, Lu, Merinov, Boris V., and Goddard, III, William A. Explanation of Dramatic pH-Dependence of Hydrogen Binding on Noble Metal Electrode: Greatly Weakened Water Adsorption at High pH. United States: N. p., 2018.
Web. doi:10.1021/jacs.8b04006.
Cheng, Tao, Wang, Lu, Merinov, Boris V., & Goddard, III, William A. Explanation of Dramatic pH-Dependence of Hydrogen Binding on Noble Metal Electrode: Greatly Weakened Water Adsorption at High pH. United States. doi:10.1021/jacs.8b04006.
Cheng, Tao, Wang, Lu, Merinov, Boris V., and Goddard, III, William A. Thu .
"Explanation of Dramatic pH-Dependence of Hydrogen Binding on Noble Metal Electrode: Greatly Weakened Water Adsorption at High pH". United States. doi:10.1021/jacs.8b04006. https://www.osti.gov/servlets/purl/1467598.
@article{osti_1467598,
title = {Explanation of Dramatic pH-Dependence of Hydrogen Binding on Noble Metal Electrode: Greatly Weakened Water Adsorption at High pH},
author = {Cheng, Tao and Wang, Lu and Merinov, Boris V. and Goddard, III, William A.},
abstractNote = {Hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER) are both 2 orders slower in alkaline electrolyte than in acidic electrolyte, but no explanation has been provided. The first step toward understanding this dramatic pH-dependent HOR/HER performance is to explain the pH-dependent hydrogen binding to the electrode, a perplexing behavior observed experimentally. In this work, we carried out Quantum Mechanics Molecular Dynamics (QMMD) with explicit considerations of solvent and applied voltage (U) to in situ simulate water/Pt(100) interface in the condition of under-potential adsorption of hydrogen (HUPD). We found that as U is made more negative, the electrode tends to repel water, which in turn increases the hydrogen binding. We predicted a 0.13 eV increase in hydrogen binding from pH = 0.2 to pH = 12.8 with a slope of 10 meV/pH, which is close to the experimental observation of 8 to 12 meV/pH. Thus, we conclude that the changes in water adsorption are the major causes of pH-dependent hydrogen binding on a noble metal. Furthermore, the new insight of critical role of surface water in modifying electrochemical reactions provides a guideline in designing HER/HOR catalyst targeting for the alkaline electrolyte.},
doi = {10.1021/jacs.8b04006},
journal = {Journal of the American Chemical Society},
number = 25,
volume = 140,
place = {United States},
year = {2018},
month = {5}
}
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