Abstract
The support-metal interaction is an important element of heterogeneous catalyst design and is particularly critical for the rapidly growing field of single-atom catalysts (SACs). We investigate the impact of varying the defect density of the titania support on metal-organic Pt SACs for hydrosilylation reactions. Pt SACs are decorated on the powder titania support, employing a metal-ligand interaction with a dipyridyl-tetrazine ligand (DPTZ). The single-atom nature of Pt is verified by X-ray absorption spectroscopy (XAS) on both pristine and defective titania surfaces. These Pt species have a +2 oxidation state and are stabilized by bonding with DPTZ, surface oxygen, and residual chloride from the metal precursor. The catalytic activity is evaluated for the alkene hydrosilylation reaction and it is discovered that the activity of Pt-ligand is positively correlated with the defect density of the titania support. The turn-over number (TON) is calculated to be 12 530 for Pt SACs on a defective surface, which is significantly higher than Pt SACs on a pristine titania surface (830) for the same reaction period (10 min) under the same conditions (70 °C). We ascribe the high activity of Pt SACs on defective titania surfaces to two aspects: the coordination of Pt with more chloride than on pristine titania surfaces, which shortens the induction period of the reaction, and the preferential dispersion of Pt-DPTZ units on defective regions of titania surfaces, allowing facile contact between Pt sites and reactants. The supported Pt-DPTZ SACs show high stability through multiple cycles of batch reactions. This work demonstrates an efficient approach to improve the activity and stability of SACs by optimizing the metal-support interaction, which can also be applied to other oxide surfaces to further develop next-generation heterogeneous single-atom catalysts.
| Original language | English |
|---|---|
| Pages (from-to) | 3353-3365 |
| Number of pages | 13 |
| Journal | Catalysis Science and Technology |
| Volume | 10 |
| Issue number | 10 |
| DOIs | |
| State | Published - May 21 2020 |
Funding
This work was supported by the U. S. Department of Energy, Office of Basic Energy Sciences, Chemical Sciences program, DE-SC0016367. XPS measurements were carried out at the Indiana University (IU) Nanoscale Characterization Facility, with assistance from Dr. Yaroslav Lasovyj. XAS measurements were performed at beamline 9-BM at the Advanced Photon Source, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science by Argonne National Laboratory, under Contract No. DE-AC02-06CH11357. Scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS) measurements were conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility. GC-MS measurements were carried out at the IU Mass Spectrometry Facility, with assistance from Dr. Jonathan A. Karty. ICP-MS measurements were performed in IU Department of Earth and Atmospheric Sciences by Benjamin Underwood. The authors thank Mackenzie Fahey for assistance with Raman spectroscopy measurements.
| Funders | Funder number |
|---|---|
| DOE Office of Science | |
| Mackenzie Fahey | |
| Office of Basic Energy Sciences | DE-SC0016367 |
| U. S. Department of Energy | |
| U.S. Department of Energy | |
| Office of Science | |
| Argonne National Laboratory | DE-AC02-06CH11357 |
| Indiana University |