期刊
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
卷 140, 期 25, 页码 7787-7790出版社
AMER CHEMICAL SOC
DOI: 10.1021/jacs.8b04006
关键词
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资金
- National Science Foundation [CBET 1512759, ACI-1053575]
- Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub through the Office of Science of the U.S. Department of Energy [DE-SC0004993]
- Div Of Chem, Bioeng, Env, & Transp Sys
- Directorate For Engineering [1512759] Funding Source: National Science Foundation
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.
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