Abstract
Identifying the rate-controlling steps and the evolution of the ligand environment throughout the catalytic cycle on supported single-atom catalysts is crucial to bridge the gap between heterogeneous and homogeneous catalysis. Here we identified the rate-controlling elementary steps for CO oxidation on TiO2-supported Ir single atoms and isolated the corresponding intermediate Ir complexes. Kinetic measurements, operando spectroscopy, and quantum-chemical calculations indicate that the reaction mechanism has two kinetically relevant steps, CO adsorption/oxidation and O2 dissociation. By varying the reaction conditions, three Ir1 complexes (states) along the reaction cycle were isolated and identified using in situ spectroscopy. Furthermore, we show that all the intermediate Ir1 states share a common CO ligand that does not turn over. This study provides atomic level details on the active, intermediate complexes and reaction cycle of supported single-metal-atom catalysts, thereby offering future possibilities to control the ligand environment and reactivity.
| Original language | English |
|---|---|
| Pages (from-to) | 7802-7811 |
| Number of pages | 10 |
| Journal | ACS Catalysis |
| Volume | 13 |
| Issue number | 12 |
| DOIs | |
| State | Published - Jun 16 2023 |
Funding
This research was primarily sponsored by the Army Research Office and was accomplished under Grant No. W911NF-19-1-0308. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressed or implied, of the Army Research Office or the U.S. Government. The U.S. Government is authorized to reproduce and distribute reprints for Government purposes notwithstanding any copyright notation herein. This research used beamline 08-ID (ISS) of the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No. DE-SC0012704. Use of the Stanford Synchrotron Radiation Light Source (SSRL, beamline 9-3, user proposal 4645), SLAC National Accelerator Laboratory, is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. DE-AC02-76SF00515. Additional support by the Consortium for Operando and Advanced Catalyst Characterization via Electronic Spectroscopy and Structure (Co-ACCESS) at SLAC is acknowledged. Co-ACCESS is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Chemical Sciences, Geosciences and Biosciences, under Contract DE-AC02-76SF00515. STEM imaging was conducted as part of a user project at the Center for Nanophase Materials Sciences (CNMS), which is a U.S. Department of Energy, Office of Science User Facility, at Oak Ridge National Laboratory. The computational resource used in this work was provided by the advanced research computing at Virginia Polytechnic Institute and State University.
Keywords
- CO oxidation
- X-ray absorption spectroscopy
- in situ
- infrared spectroscopy
- ligand chemistry
- operando
- single-atom catalysis