Electrocatalytic systems based on metal-organic frameworks (MOFs) have attracted great attention due to their potential application in commercially viable renewable energy-converting devices. We have recently shown that the cobalt 2,3,6,7,10,11-triphenylenehexathiolate (CoTHT) framework can catalyze the hydrogen evolution reaction (HER) in fully aqueous media with Tafel slopes as low as 71 mV/dec and near-unity Faradaic efficiency (FE). Taking advantage of the high synthetic tunability of MOFs, here, we synthesize a series of iron and mixed iron/cobalt THT-based MOFs. The incorporation of the iron and cobalt dithiolene moieties is verified by various spectroscopic techniques, and the integrity of the crystalline structure is maintained regardless of the stoichiometries of the two metals. The hydrogen evolving activity of the materials was explored in pH 1.3 aqueous electrolyte solutions. Unlike CoTHT, the FeTHT framework exhibits minimal activity due to a late catalytic onset [-0.440 V versus reversible hydrogen electrode (RHE)] and a large Tafel slope (210 mV/dec). The performance of the mixed-metal MOFs is adversely affected by the incorporation of Fe, where increasing Fe content results in MOFs with lower HER activity and diminished long-term stability and FE for H2 production. It is proposed that the FeTHT domains undergo alternative Faradaic processes under catalytic conditions, which alter its local structure and electrochemical behavior, eventually resulting in a material with diminished HER performance.
|Original language||English (US)|
|Number of pages||9|
|State||Published - Aug 16 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. Additional support was provided by the National Science Foundation under award DMR-2004868 (FTIR experimental studies) and by the U. S. Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences under Award DE-FG02-17ER16362 (FTIR theoretical studies). K.C. gratefully acknowledges the University of Southern California (USC) Wrigley Institute for the Norma and Jerol Sonosky summer fellowship. 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 No. DE-AC02-06CH11357. XPS and SEM data were collected at the Core Center of Excellence in Nano Imaging, USC. The authors thank Dr. Andrew J. Clough for assistance with the collection of the SEM images. J.D.G. acknowledges the Minnesota Supercomputing Institute (MSI) at the University of Minnesota and the National Energy Research Scientific Computing Center (NERSC), a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231, for providing resources that contributed to the computational results reported within this paper.
© 2021 American Chemical Society.
PubMed: MeSH publication types
- Journal Article