| AVS 58th Annual International Symposium and Exhibition | |
| Thin Film Division | Tuesday Sessions |
| Session TF+EN-TuM |
| Session: | ALD for Energy |
| Presenter: | Virginia R. Anderson, University of Colorado, Boulder |
| Authors: | V.R. Anderson, University of Colorado, Boulder N. Leick, Eindhoven University of Technology, Netherlands K.E. Hurst, National Renewable Energy Laboratory A.S. Cavanagh, University of Colorado, Boulder S. Kocha, National Renewable Energy Laboratory K. Jones, National Renewable Energy Laboratory A.C. Dillon, National Renewable Energy Laboratory S.M. George, University of Colorado, Boulder |
| Correspondent: | Click to Email |
Platinum nanoparticles are used as the catalyst on the cathodes of proton exchange membrane (PEM) fuel cells. Controlling the dispersion and size of the Pt nanoparticles is important for efficient and cost-effective fuel cells. When Pt atomic layer deposition (ALD) is performed on oxide or carbon substrates, nucleation difficulties and the high surface energy of Pt lead to Pt nanoparticles rather than continuous films. This research explored strategies to control the dispersion and size of Pt nanoparticles using Pt ALD together with various surface treatments. Pt ALD was performed using Pt hexafluoroacetylacetonate Pt(hfac)2 and formalin as the reactants. Titanium oxide (TiO2) and tungsten oxide (WO3) were explored as the substrates. We used in situ transmission Fourier transform infrared (FTIR) spectroscopy to monitor the surface species during Pt ALD. Surface poisoning by hfac species was observed during the nucleation of Pt ALD on TiO2, in agreement with our previous studies of Pd ALD [1]. Trimethylaluminum (TMA) was able to remove the hfac species from TiO2 and promote more facile nucleation of Pt ALD, also as expected by our earlier work on Pd ALD [2]. We then used hfacH adsoption prior to Pt ALD to block surface sites, delay Pt ALD nucleation and decrease Pt nanoparticle dispersion. In addition, we used TMA exposures after Pt(hfac)2 exposures to facilitate Pt ALD nucleation and increase Pt nanoparticle dispersion. The Pt nanoparticles were detected by the rising absorbance baseline of the FTIR spectrum, and transmission electron microscopy images of Pt nanoparticles on TiO2 and WO3 particles. The size of the Pt nanoparticles was dependent on the number of ALD reaction cycles.
1. D.N. Goldstein & S.M. George, Thin Solid Films (In Press).
2. D.N. Goldstein & S.M. George, Appl. Phys. Lett. 95, 143106 (2009).