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Visible Light Photolysis at Single Atom Sites in Semiconductor Perovskite Oxides
Michael G Allan1, Rachel A Yang1, Silvia Marino2
1Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan 48109, United States.
Journal of the American Chemical Society
|December 27, 2024
Summary
Visible light activates rhodium catalysts in perovskite oxides to remove carbon monoxide (CO) at mild temperatures. This overcomes limitations of UV-activated catalysts, enabling efficient CO photodepletion and stable catalytic cycles.
Area of Science:
- Heterogeneous Catalysis
- Materials Science
- Photochemistry
Background:
- Catalytic reactions are often limited by scaling relations on heterogeneous surfaces.
- Carbon monoxide (CO) can poison active sites by forming stable complexes with metals like rhodium (Rh).
- Existing methods for CO photodepletion from Rh sites typically require high-energy UV photons.
Purpose of the Study:
- To design catalysts with visible-light-responsive active sites for overcoming catalytic limitations.
- To demonstrate the removal of strongly bound CO from well-defined Rh sites under mild conditions using visible light.
- To elucidate the distinct mechanisms of CO photodepletion in different catalytic systems.
Main Methods:
- Incorporating single Rh sites into a photoactive perovskite oxide (Rh-doped SrTiO3).
- Investigating CO removal under visible red light (635 nm) irradiation at 323 K.
- Conducting rigorous kinetic experiments to compare Rh-doped SrTiO3 with supported isolated-site Rh/γ-Al2O3 catalysts.
- Analyzing electronic excitation mechanisms via midgap energy states.
Main Results:
- CO removal from Rh-doped SrTiO3 was achieved at mild temperatures (323 K) using low-energy red light, unlike supported Rh catalysts.
- Distinct photodepletion mechanisms were identified: direct metal-to-ligand charge transfer for Rh/γ-Al2O3 and electron-hole pair formation for Rh-doped SrTiO3.
- Visible light induces electronic excitations in Rh-doped SrTiO3 via midgap states, facilitating CO removal.
- Isolated Rh sites in Rh-doped SrTiO3 showed excellent stability during multiple CO photodepletion cycles.
Conclusions:
- Incorporating single Rh sites into photoactive perovskite oxides is an effective strategy for visible-light-driven surface chemistry.
- This approach overcomes limitations of UV-dependent photolysis and enables mild-temperature CO removal.
- The findings offer a pathway to design advanced catalysts that overcome scaling relations in chemical reactions.
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