Journal
ACS CATALYSIS
Volume 8, Issue 6, Pages 4751-4760Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acscatal.7b04173
Keywords
heterogeneous catalysts; palladium; CO oxidation; strontium titanate; atomic layer deposition; X-ray small angle scattering; X-ray absorption near edge structure; diffuse reflectance infrared Fourier transform spectroscopy
Categories
Funding
- Institute for Catalysis in Energy Processes (ICEP) at Northwestern University (NU) under DOE Grant [DE-FG02-03ER1S457]
- E.I. DuPont de Nemours Co.
- NU
- Dow Chemical Co.
- DOE [DE-AC02-06CH11357]
- NU-MRSEC program [NSF DMR-1720139]
- MRI-R2 grant from the National Science Foundation [NSF DMR-0959470]
- U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences [DE-AC02-06CH11357]
- Department of Energy [DE-AC02-06CH11357, DE-FG02-03ER15457]
- Study Abroad Fellowship from Ministry of Education of Taiwan
- National Science Foundation Graduate Research Fellowship
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Single crystal SrTiO3 nanocuboids having primarily TiO2-(001) surfaces and nanododecahedra having primarily (110) surfaces were created by two separate hydrothermal synthesis processes. Pd nanoparticles grown on the two sets of STO nanopolyhedra by atomic layer deposition show different morphologies and CO oxidation performance. Transmission electron microscopy and small-angle X-ray scattering show that 2-3 nm Pd nanoparticles with 3-5 nm interparticle distances decorate the STO surfaces. When the number of ALD cycles increases, the growth of the Pd nanoparticles is more significant in size on TiO2-(001)-STO surfaces, while that on (110)-STO surfaces is more predominant in number. High resolution electron microscopy images show that single crystal and multiply twinned Pd nanoparticles coexist on both types of the STO nanopolyhedra and exhibit different degrees of adhesion. The CO oxidation reaction, which was employed to determine the dependence of catalytic activity, showed that the Pd catalytic performance was dominated by the coverage of CO, which is more directly related to Pd nanoparticle size than to shape. CO turnover frequency analysis and diffuse reflectance infrared Fourier transform spectroscopy show that regardless of the shape or degrees of wetting, larger Pd nanoparticles (similar to 3 nm) have lower catalytic activity due to high CO coverage on nanoparticle facets. Smaller nanoparticles (similar to 2 nm) have more edge and corner sites and exhibit 2-3 times higher TOF at 80 and 100 degrees C.
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