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Field Effect Modulation of Electrocatalytic Hydrogen Evolution at Back-Gated Two-Dimensional MoS2 Electrodes

preprint
submitted on 19.05.2019 and posted on 20.05.2019 by Yan Wang, Sagar Udyavara, Matthew Neurock, C. Daniel Frisbie

Electrocatalytic activity for hydrogen evolution at monolayer MoS2 electrodes can be enhanced by the application of an electric field normal to the electrode plane. The electric field is produced by a gate electrode lying underneath the MoS2 and separated from it by a dielectric. Application of a voltage to the back-side gate electrode while sweeping the MoS2 electrochemical potential in a conventional manner in 0.5 M H2SO4 results in up to a 140-mV reduction in overpotential for hydrogen evolution at current densities of 50 mA/cm2. Tafel analysis indicates that the exchange current density is correspondingly improved by a factor of 4 to 0.1 mA/cm2 as gate voltage is increased. Density functional theory calculations support a mechanism in which the higher hydrogen evolution activity is caused by gate-induced electronic charge on Mo metal centers adjacent the S vacancies (the active sites), leading to enhanced Mo-H bond strengths. Overall, our findings indicate that the back-gated working electrode architecture is a convenient and versatile platform for investigating the connection between tunable electronic charge at active sites and overpotential for electrocatalytic processes on ultrathin electrode materials.


History

Email Address of Submitting Author

wang5502@umn.edu

Institution

University of Minnesota

Country

United States

ORCID For Submitting Author

0000-0003-1264-3794

Declaration of Conflict of Interest

No Conflict of Interest

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