Abstract
Single-atom catalysts (SACs) often exhibit dynamic responses to the reaction and pretreatment environment that affect their activity. The lack of understanding of these behaviors hinders the development of effective, stable SACs, and makes their investigations rather difficult. Here we report a reduction-oxidation cycle that induces nearly 5-fold activity enhancement on Pt/TiO2SACs for the reverse water-gas shift (rWGS) reaction. We combine microscopy (STEM) and spectroscopy (XAS and IR) studies with kinetic measurements, to convincingly show that the low activity on the fresh SAC is a result of limited accessibility of Pt single atoms (Pt1) due to high Pt-O coordination. The reduction step mobilizes Pt1, forming small, amorphous, and unstable Pt aggregates. The reoxidation step redisperses Pt into Pt1, but in a new, less O-coordinated chemical environment that makes the single metal atoms more accessible and, consequently, more active. After the cycle, the SAC exhibits superior rWGS activity to nonatomically dispersed Pt/TiO2. During the rWGS, the activated Pt1experience slow deactivation, but can be reactivated by mild oxidation. This work demonstrates a clear picture of how the structural evolution of Pt/TiO2SACs leads to ultimate catalytic efficiency, offering desired understanding on the rarely explored dynamic chemical environment of supported single metal atoms and its catalytic consequences.
| Original language | English |
|---|---|
| Pages (from-to) | 977-986 |
| Number of pages | 10 |
| Journal | JACS Au |
| Volume | 1 |
| Issue number | 7 |
| DOIs | |
| State | Published - Jul 26 2021 |
Funding
This work was supported by the U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences, and performed at the Environmental Molecular Sciences Laboratory in (EMSL), which is a DOE Office of Science User Facility located at Pacific Northwest National Laboratory (PNNL). PNNL is a multiprogram national laboratory operated for DOE by Battelle. We acknowledge Dr. Mark E. Bowden, X. Shari Li, and Dr. Libor Kovarik at PNNL for XRD, BET, and supplemental STEM measurements. STEM imaging in the manuscript was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility. Use of the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract DE-AC02-76SF00515. Co-ACCESS is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Chemical Sciences, Geosciences and Bioscience Division. This research used resources of the Advanced Photon Source (APS), an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science by Argonne National Laboratory, and was supported by the U.S. DOE under Contract DE-AC02-06CH11357, and the Canadian Light Source and its funding partners. We acknowledge Dr. Debora Meira at the APS for supplemental XAS measurements. A.H.B. acknowledges RCGI – Research Centre for Gas Innovation, hosted by the University of São Paulo (USP) and sponsored by FAPESP–São Paulo Research Foundation (2014/50279-4) and Shell Brasil.
| Funders | Funder number |
|---|---|
| U.S. Department of Energy | DE-AC02-06CH11357 |
| Office of Science | |
| Basic Energy Sciences | |
| Argonne National Laboratory | |
| Canadian Light Source | |
| Pacific Northwest National Laboratory | DE-AC02-76SF00515 |
| Chemical Sciences, Geosciences, and Biosciences Division | |
| Shell United States | |
| Research Centre for Gas Innovation | |
| Fundação de Amparo à Pesquisa do Estado de São Paulo | 2014/50279-4 |
Keywords
- COhydrogenation
- platinum
- reverse water-gas shift
- single-atom catalyst
- titania
