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This content will become publicly available on December 27, 2018

Title: Balancing the Hydrogen Evolution Reaction, Surface Energetics, and Stability of Metallic MoS 2 Nanosheets via Covalent Functionalization

We modify the fundamental electronic properties of metallic (1T phase) nanosheets of molybdenum disulfide (MoS 2) through covalent chemical functionalization, and thereby directly influence the kinetics of the hydrogen evolution reaction (HER), surface energetics, and stability. Chemically exfoliated, metallic MoS 2 nanosheets are functionalized with organic phenyl rings containing electron donating or withdrawing groups. We find that MoS 2 functionalized with the most electron donating functional group (p-(CH 3CH 2) 2NPh-MoS 2) is the most efficient catalyst for HER in this series, with initial activity that is slightly worse compared to the pristine metallic phase of MoS 2. The p-(CH 3CH 2) 2NPh-MoS 2 is more stable than unfunctionalized metallic MoS 2 and outperforms unfunctionalized metallic MoS 2 for continuous H 2 evolution within 10 min under the same conditions. With regards to the entire studied series, the overpotential and Tafel slope for catalytic HER are both directly correlated with the electron donating strength of the functional group. The results are consistent with a mechanism involving ground-state electron donation or withdrawal to/from the MoS 2 nanosheets, which modifies the electron transfer kinetics and catalytic activity of the MoS 2 nanosheet. The functional groups preserve the metallic nature of the MoSmore » 2 nanosheets, inhibiting conversion to the thermodynamically stable semiconducting state (2H) when mildly annealed in a nitrogen atmosphere. We propose that the electron density and, therefore, reactivity of the MoS 2 nanosheets are controlled by the attached functional groups. Functionalizing nanosheets of MoS 2 and other transition metal dichalcogenides provides a synthetic chemical route for controlling the electronic properties and stability within the traditionally thermally unstable metallic state.« less
Authors:
ORCiD logo [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1] ; ORCiD logo [1] ; ORCiD logo [1]
  1. National Renewable Energy Lab. (NREL), Golden, CO (United States)
Publication Date:
Report Number(s):
NREL/JA-5900-68922
Journal ID: ISSN 0002-7863
Grant/Contract Number:
AC36-08GO28308
Type:
Accepted Manuscript
Journal Name:
Journal of the American Chemical Society
Additional Journal Information:
Journal Volume: 140; Journal Issue: 1; Journal ID: ISSN 0002-7863
Publisher:
American Chemical Society (ACS)
Research Org:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); USDOE Office of Science (SC), Workforce Development for Teachers and Scientists (WDTS) (SC-27)
Country of Publication:
United States
Language:
English
Subject:
08 HYDROGEN; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; electronic properties; functionalization; hydrogen evolution reaction; surface energetics; stability
OSTI Identifier:
1416526