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The Reaction Mechanism for the Hydrogen Evolution Reaction on the Basal Plane Sulfur Vacancy Site of MoS_2 Using Grand Canonical Potential Kinetics

Huang, Yufeng and Nielsen, Robert J. and Goddard, William A., III (2018) The Reaction Mechanism for the Hydrogen Evolution Reaction on the Basal Plane Sulfur Vacancy Site of MoS_2 Using Grand Canonical Potential Kinetics. Journal of the American Chemical Society, 140 (48). pp. 16773-16782. ISSN 0002-7863. doi:10.1021/jacs.8b10016.

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We develop the grand canonical potential kinetics (GCP-K) formulation based on thermodynamics from quantum mechanics calculations to provide a fundamental basis for understanding heterogeneous electrochemical reactions. Our GCP-K formulation arises naturally from minimizing the free energy using a Legendre transform relating the net charge of the system and the applied voltage. Performing this macroscopic transformation explicitly allows us to make the connection of GCP-K to the traditional Butler–Volmer kinetics. Using this GCP-K based free energy, we show how to predict both the potential and pH dependent chemistry for a specific example, the hydrogen evolution reaction (HER) at a sulfur vacancy on the basal plane of MoS_2. We find that the rate-determining steps in both acidic and basic conditions are the Volmer reaction in which the second hydrogen atom is adsorbed from the solution. Using the GCP-K formulation, we show that the stretched bond distances change continuously as a function of the applied potential. This shows that the main reason for the higher activity in basic conditions is that the transition state is closer to the product, which leads to a more favorable Tafel slope of 60 mV/dec. In contrast if the transition state were closer to the reactant, where the transfer coefficient is less than 0.5 we would obtain a Tafel slope of almost 150 mV/dec. Based on this detailed understanding of the reaction mechanism, we conclude that the second hydrogen at the chalcogenide vacant site is the most active toward the hydrogen evolution reaction. Using this as a descriptor, we compare it to the other 2H group VI metal dichalcogenides and predict that vacancies on MoTe_2 will have the best performance toward HER.

Item Type:Article
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URLURL TypeDescription Information
Huang, Yufeng0000-0002-0373-2210
Nielsen, Robert J.0000-0002-7962-0186
Goddard, William A., III0000-0003-0097-5716
Additional Information:© 2018 American Chemical Society. Received: September 14, 2018; Published: November 8, 2018. This work was supported by 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 Number DE-SC0004993. This work uses the resource of National Energy Research Scientific Computing center (NERSC). The authors declare no competing financial interest.
Funding AgencyGrant Number
Department of Energy (DOE)DE-SC0004993
Subject Keywords:Electrochemistry, Grand Canonical Potential, Hydrogen Evolution Reaction, Molybdenum Disulfide
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Issue or Number:48
Record Number:CaltechAUTHORS:20181108-141108999
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Official Citation:Reaction Mechanism for the Hydrogen Evolution Reaction on the Basal Plane Sulfur Vacancy Site of MoS2 Using Grand Canonical Potential Kinetics. Yufeng Huang, Robert J. Nielsen, and William A. Goddard, III Journal of the American Chemical Society 2018 140 (48), 16773-16782. DOI: 10.1021/jacs.8b10016
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:90764
Deposited By: Tony Diaz
Deposited On:09 Nov 2018 04:13
Last Modified:16 Nov 2021 03:35

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