(273e) Preparation of Carbon Supported Pt Nanoparticles By Atomic Layer Deposition
Hydrogen fuel cells offer an efficient use of a more energy dense fuel compared to combustion engines using gasoline. However, adaptation of fuel cells to power vehicles depends on several factors, one of which is economic synthesis of each component. Atomic layer deposition (ALD) using a fluidized bed reactor is an economic and scalable method for manufacturing the noble metal nanoparticle catalyst. This work furthers understanding of reported mechanisms of platinum ALD by investigating reactions on a common carbon support, XC72-R. By-products of reactions during ALD using trimethyl(methylcyclopentadienyl)platinum(IV) (MeCpPtMe3) and either oxygen or hydrogen as reactants on un-modified carbon and carbon functionalized using nitric acid are inspected using in situ mass spectrometry. This understanding will help fine-tune parameters during a commercial catalyst synthesis process. Platinum weight loading, average particle size and particle dispersion depend on the chemistry of the pre-processing and precursor reactions. Oxygen becomes integrated into the carbon during functionalization and binds platinum tighter than just carbon; therefore particles aggregate less during deposition on functionalized carbon. Combustion of the ligand of MeCpPtMe3 attached to carbon, as well as substrate oxidation during the oxygen dose, contribute to more particle aggregation versus when hydrogen is utilized for ligand removal. Mechanisms for each ALD condition are proposed.