Despite the promising previous reports on the development of electrocatalytic dithiolene-based metal-organic frameworks (MOFs) for the hydrogen evolution reaction (HER), these materials often display poor reproducibility of the HER performance because of their poor bulk properties upon integration with electrode materials. We demonstrate here an in-depth investigation of the electrocatalytic HER activity of a cobalt 2,3,6,7,10,11-triphenylenehexathiolate (CoTHT) MOF. To enhance the durability and charge transport properties of the constructed CoTHT/electrode architecture, CoTHT is deposited as an ink composite (1) composed of Nafion and carbon black. We leverage here the well-established use of catalyst inks in the literature to increase adhesion of the catalyst to the electrode surface and to improve the overall electrical conductivity of the integrated catalyst/electrode. The utilization of the composite 1 leads to a significant improvement in the overpotential (η) to reach a current density of 10 mA/cm2 (η = 143 mV) compared to prior reports, resulting in the most active MOF-based electrocatalyst for the HER that contains only earth-abundant elements. Extensive density functional theory (DFT) calculations were applied to understand the structure of CoTHT and the mechanistic pathways of the HER. The computational results suggest that an AB stacking geometry is energetically favorable, where one layer is slipped by 1.6 Å relative to the neighboring one along the a and b vectors. Additionally, the DFT calculations indicate that the catalytic cycle likely involves a Volmer discharge step to generate a cobalt hydride, followed by a Heyrovsky step to form a cobalt-H2 intermediate, and finally the dissociation of H2.
|Original language||English (US)|
|Number of pages||12|
|Journal||ACS Applied Materials and Interfaces|
|State||Published - Apr 14 2021|
Bibliographical noteFunding Information:
The research was primarily supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences, under Award DE-SC0019236 (experimental studies) and the Nanoporous Materials Genome Center, funded by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences, under Award DE-FG02-17ER16362 (theoretical studies). Additional support was provided by the University of Southern California (USC), the USC Women in Science and Engineering, and the University of Minnesota. K.C. gratefully acknowledges the USC Dana and David Dornsife College of Letters, Arts and Sciences for a research fellowship, and the USC Wrigley Institute for the Norma and Jerol Sonosky summer fellowship. An award of computer time was provided by the ASCR Leadership Computing Challenge (ALCC) program. This research used resources of the National Energy Research Scientific Computing Center (NERSC), a U.S. Department of Energy Office of Science User Facility operated under Contract DE-AC02-05CH11231. Additional computer resources were provided by the Minnesota Supercomputing Institute (MSI) at the University of Minnesota. Use of the Advanced Photon Source at Argonne National Laboratory was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract DE-AC02-06CH11357. XPS and SEM data were collected at the Core Center of Excellence in Nano Imaging, USC. We thank Dr. Andrew J. Clough for assistance with the collection of the SEM images.
© 2021 American Chemical Society.
- DFT calculations
- cobalt dithiolene
- hydrogen evolution
- metal-organic framework