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Determining the hydronium pKα at platinum surfaces and the effect on pH-dependent hydrogen evolution reaction kinetics

Zhong, Guangyan and Cheng, Tao and Shah, Aamir Hassan and Wan, Chengzhang and Huang, Zhihong and Wang, Sibo and Leng, Tianle and Huang, Yu and Goddard, William A., III and Duan, Xiangfeng (2022) Determining the hydronium pKα at platinum surfaces and the effect on pH-dependent hydrogen evolution reaction kinetics. Proceedings of the National Academy of Sciences of the United States of America, 119 (39). Art. No. e2208187119. ISSN 0027-8424. doi:10.1073/pnas.2208187119. https://resolver.caltech.edu/CaltechAUTHORS:20221011-984569000.2

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Abstract

Electrocatalytic hydrogen evolution reaction (HER) is critical for green hydrogen generation and exhibits distinct pH-dependent kinetics that have been elusive to understand. A molecular-level understanding of the electrochemical interfaces is essential for developing more efficient electrochemical processes. Here we exploit an exclusively surface-specific electrical transport spectroscopy (ETS) approach to probe the Pt-surface water protonation status and experimentally determine the surface hydronium pKa = 4.3. Quantum mechanics (QM) and reactive dynamics using a reactive force field (ReaxFF) molecular dynamics (RMD) calculations confirm the enrichment of hydroniums (H3O+*) near Pt surface and predict a surface hydronium pKa of 2.5 to 4.4, corroborating the experimental results. Importantly, the observed Pt-surface hydronium pKa correlates well with the pH-dependent HER kinetics, with the protonated surface state at lower pH favoring fast Tafel kinetics with a Tafel slope of 30 mV per decade and the deprotonated surface state at higher pH following Volmer-step limited kinetics with a much higher Tafel slope of 120 mV per decade, offering a robust and precise interpretation of the pH-dependent HER kinetics. These insights may help design improved electrocatalysts for renewable energy conversion.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1073/pnas.2208187119DOIArticle
https://www.pnas.org/doi/10.1073/pnas.2208187119#supplementary-materialsPublisherSupporting Information
ORCID:
AuthorORCID
Cheng, Tao0000-0003-4830-177X
Shah, Aamir Hassan0000-0002-0471-4575
Huang, Yu0000-0003-1793-0741
Goddard, William A., III0000-0003-0097-5716
Duan, Xiangfeng0000-0002-4321-6288
Additional Information:X.D. acknowledges support from NSF Award 1800580. Y.H. acknowledges the gracious support by NewHydrogen, Inc. W.A.G. received support from the Liquid Sunlight Alliance, which is supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, Fuels from Sunlight Hub under Award DE-SC0021266. T.C. acknowledges support from the National Natural Science Foundation of China (21903058 and 22173066),the Natural Science Foundation of Jiangsu Higher Education Institutions(BK20190810), and the Priority Academic Program Development of Jiangsu Higher Education Institutions and partial support from the Collaborative Innovation Center of Suzhou NanoScience & Technology. Portions of this paper were used in the PhD thesis of G.Z.
Group:Liquid Sunlight Alliance
Funders:
Funding AgencyGrant Number
NSFCHE-1800580
Department of Energy (DOE)DE-SC0021266
National Natural Science Foundation of China21903058
National Natural Science Foundation of China22173066
Natural Science Foundation of Jiangsu ProvinceBK20190810
Priority Academic Program Development of Jiangsu Higher Education InstitutionsUNSPECIFIED
Collaborative Innovation Center of Suzhou NanoScience & TechnologyUNSPECIFIED
NewHydrogen, Inc.UNSPECIFIED
Other Numbering System:
Other Numbering System NameOther Numbering System ID
WAG1539
Issue or Number:39
DOI:10.1073/pnas.2208187119
Record Number:CaltechAUTHORS:20221011-984569000.2
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20221011-984569000.2
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:117364
Collection:CaltechAUTHORS
Deposited By: Donna Wrublewski
Deposited On:12 Oct 2022 18:18
Last Modified:12 Oct 2022 22:18

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