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Comparative Study in Acidic and Alkaline Media of the Effects of pH and Crystallinity on the Hydrogen-Evolution Reaction on MoS_2 and MoSe_2

Wiensch, Joshua D. and John, Jimmy and Velazquez, Jesus M. and Torelli, Daniel A. and Pieterick, Adam P. and McDowell, Matthew T. and Sun, Ke and Zhao, Xinghao and Brunschwig, Bruce S. and Lewis, Nathan S. (2017) Comparative Study in Acidic and Alkaline Media of the Effects of pH and Crystallinity on the Hydrogen-Evolution Reaction on MoS_2 and MoSe_2. ACS Energy Letters, 2 (10). pp. 2234-2238. ISSN 2380-8195. https://resolver.caltech.edu/CaltechAUTHORS:20170907-124508456

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Abstract

Single crystals of n-type MoS_2 and n-MoSe_2 showed higher electrocatalytic activity for the evolution of H_2(g) in alkaline solutions than in acidic solutions. The overpotentials required to drive hydrogen evolution at −10 mA cm^(–2) of current density for MoS^2 samples were −0.76 ± 0.13 and −1.03 ± 0.21 V when in contact with 1.0 M NaOH(aq) and 1.0 M H_2SO_4(aq), respectively. For MoSe_2 samples, the overpotentials at −10 mA cm^(–2) were −0.652 ± 0.050 and −0.709 ± 0.073 V in contact with 1.0 M KOH(aq) and 1.0 M H_2SO_4(aq), respectively. Single crystals from two additional sources were also tested, and the absolute values of the measured overpotentials were consistently less (by 460 ± 250 mV) in alkaline solutions than in acidic solutions. When electrochemical etching was used to create edge sites on the single crystals, the kinetics improved in acid but changed little in alkaline media. The overpotentials measured for polycrystalline thin films (PTFs) and amorphous forms of MoS_2 showed less sensitivity to pH and edge density than was observed for single crystals and showed enhanced kinetics in acid when compared to alkaline solutions. These results suggest that the active sites for hydrogen evolution on MoS_2 and MoSe_2 are different in alkaline and acidic media. Thus, while edges are known to serve as active sites in acidic media, in alkaline media it is more likely that terraces function in this role.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://dx.doi.org/10.1021/acsenergylett.7b00700DOIArticle
http://pubs.acs.org/doi/10.1021/acsenergylett.7b00700PublisherArticle
http://pubs.acs.org/doi/suppl/10.1021/acsenergylett.7b00700PublisherSupporting Information
ORCID:
AuthorORCID
Wiensch, Joshua D.0000-0002-8235-6937
Sun, Ke0000-0001-8209-364X
Brunschwig, Bruce S.0000-0002-6135-6727
Lewis, Nathan S.0000-0001-5245-0538
Additional Information:© 2017 American Chemical Society. Received: August 4, 2017; Accepted: August 28, 2017; Published: September 6, 2017. J.J. thanks the Camille and Henry Dreyfus Foundation for support through its postdoctoral fellowship program in environmental chemistry. This material is based upon work supported by the U.S. Department of Energy, Office of Basic Energy Sciences under Award No. DE-FG02-03ER15483. J.M.V. acknowledges support through an NRC Ford Foundation Postdoctoral Fellowship. D.A.T. acknowledges support through the NSF Graduate Research Fellowships Program. Single-crystal MoS2 growth and sputtering of Mo was performed at 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. X-ray photoelectron spectroscopy was performed at the Molecular Materials Research Center of the Beckman Institute at Caltech.
Group:JCAP
Funders:
Funding AgencyGrant Number
Camille and Henry Dreyfus FoundationUNSPECIFIED
Department of Energy (DOE)DE-FG02-03ER15483
NRC Ford Foundation Postdoctoral FellowshipUNSPECIFIED
NSF Graduate Research FellowshipUNSPECIFIED
Department of Energy (DOE)DE-SC0004993
Issue or Number:10
Record Number:CaltechAUTHORS:20170907-124508456
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20170907-124508456
Official Citation:Comparative Study in Acidic and Alkaline Media of the Effects of pH and Crystallinity on the Hydrogen-Evolution Reaction on MoS2 and MoSe2 Joshua D. Wiensch, Jimmy John, Jesus M. Velazquez, Daniel A. Torelli, Adam P. Pieterick, Matthew T. McDowell, Ke Sun, Xinghao Zhao, Bruce S. Brunschwig, and Nathan S. Lewis ACS Energy Letters 2017 2 (10), 2234-2238 DOI: 10.1021/acsenergylett.7b00700
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:81242
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:08 Sep 2017 16:48
Last Modified:03 Oct 2019 18:40

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