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Explanation of Dramatic pH-Dependence of Hydrogen Binding on Noble Metal Electrode: Greatly Weakened Water Adsorption at High pH

Cheng, Tao and Wang, Lu and Merinov, Boris V. and Goddard, William A., III (2018) Explanation of Dramatic pH-Dependence of Hydrogen Binding on Noble Metal Electrode: Greatly Weakened Water Adsorption at High pH. Journal of the American Chemical Society, 140 (25). pp. 7787-7790. ISSN 0002-7863. doi:10.1021/jacs.8b04006.

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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. 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.

Item Type:Article
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URLURL TypeDescription Information
Cheng, Tao0000-0003-4830-177X
Wang, Lu0000-0001-5263-3123
Merinov, Boris V.0000-0002-2783-4262
Goddard, William A., III0000-0003-0097-5716
Additional Information:© 2018 American Chemical Society. Received: April 22, 2018; Published: May 24, 2018. This work was initiated with support from National Science Foundation (CBET 1512759, program manager Robert McCabe) and completed with support from the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub, supported through the Office of Science of the U.S. Department of Energy under Award No. DE-SC0004993. This work used the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by National Science Foundation grant number ACI-1053575. The authors declare no competing financial interests.
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Joint Center for Artificial Photosynthesis (JCAP)UNSPECIFIED
Department of Energy (DOE)DE-SC0004993
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Issue or Number:25
Record Number:CaltechAUTHORS:20180524-100856381
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Official Citation:Explanation of Dramatic pH-Dependence of Hydrogen Binding on Noble Metal Electrode: Greatly Weakened Water Adsorption at High pH. Tao Cheng, Lu Wang, Boris V. Merinov, and William A. Goddard, III. Journal of the American Chemical Society 2018 140 (25), 7787-7790. DOI: 10.1021/jacs.8b04006
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:86586
Deposited By: Tony Diaz
Deposited On:24 May 2018 17:17
Last Modified:15 Nov 2021 20:40

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