Palladium Nanoparticle Formation on TiO 2 (110) by Thermal Decomposition of Palladium(II) Hexafluoroacetylacetonate
- School of Chemical Engineering, Purdue University, West Lafayette, Indiana 47907, United States
- School of Chemical Engineering, Purdue University, West Lafayette, Indiana 47907, United States; Boreskov Institute of Catalysis, Novosibirsk 630090, Russia; Novosibirsk State University, Novosibirsk 630090, Russia
- Energy Systems Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
Palladium nanoparticles were synthesized by thermal decomposition of palladium(II) hexafluoroacetylacetonate (Pd(hfac)2), an atomic layer deposition (ALD) precursor, on a TiO2(110) surface. According to X-ray photoelectron spectroscopy (XPS), Pd(hfac)2 adsorbs on TiO2(110) dissociatively yielding Pd(hfac)ads, hfacads, and adsorbed fragments of the hfac ligand at 300 K. A (2 × 1) surface overlayer was observed by scanning tunneling microscopy (STM), indicating that hfac adsorbs in a bidentate bridging fashion across two Ti 5-fold atoms and Pd(hfac) adsorbs between two bridging oxygen atoms on the surface. Annealing of the Pd(hfac)ads and hfacads species at 525 K decomposed the adsorbed hfac ligands, leaving PdO-like species and/or Pd atoms or clusters. Above 575 K, the XPS Pd 3d peaks shift toward lower binding energies and Pd nanoparticles are observed by STM. These observations point to the sintering of Pd atoms and clusters to Pd nanoparticles. The average height of the Pd nanoparticles was 1.2 ± 0.6 nm at 575 K and increased to 1.7 ± 0.5 nm following annealing at 875 K. The Pd coverage was estimated from XPS and STM data to be 0.05 and 0.03 monolayers (ML), respectively, after the first adsorption/decomposition cycle. The amount of palladium deposited on the TiO2(110) surface increased linearly with the number of adsorption/decomposition cycles with a growth rate of 0.05 ML or 0.6 Å per cycle. We suggest that the removal of the hfac ligand and fragments eliminates the nucleation inhibition of Pd nanoparticles previously observed for the Pd(hfac)2 precursor on TiO2.
- Research Organization:
- Energy Frontier Research Centers (EFRC) (United States). Institute for Atom-efficient Chemical Transformations (IACT)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES)
- DOE Contract Number:
- AC02-06CH11357
- OSTI ID:
- 1385883
- Journal Information:
- ACS Applied Materials and Interfaces, Vol. 6, Issue 16; Related Information: IACT partners with Argonne National Laboratory (lead); Brookhaven National Laboratory; Northwestern University; Purdue University; University of Wisconsin at Madison; ISSN 1944-8244
- Publisher:
- American Chemical Society (ACS)
- Country of Publication:
- United States
- Language:
- English
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