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Preparation of Carbon Nanofiber Supported Platinum and Ruthenium Catalysts: Comparison of Ion Adsorption and Homogeneous Deposition Precipitation

2004; American Chemical Society; Volume: 108; Issue: 31 Linguagem: Inglês

10.1021/jp0313472

1520-6106

Marjolein L. Toebes, Martijn K. van der Lee, Lai Mei Tang, Marije H. Huis in ‘t Veld, Johannes H. Bitter, A.J. van Dillen, Krijn P. de Jong,

Supercapacitor Materials and Fabrication

Carbon nanofiber (CNF) supported platinum catalysts have been prepared using Pt(NH3)4(NO3)2 as a precursor by two different ion adsorption techniques, one at a constant pH and one in which the pH is gradually and homogeneously increased from 3 to 6 by hydrolysis of urea. The latter method resembles the procedure of homogeneous deposition precipitation (HDP). Characterization of the CNF support was performed by acid−base titration, thermogravimetric mass spectrometry, and X-ray photoelectron spectroscopy, and for the various platinum catalysts, transmission electron microscopy, H2-chemisorption, and X-ray fluorescence/inductively coupled plasma-atomic emission spectrometry were utilized. With both synthesis techniques from diluted precursor solutions homogeneously distributed, highly dispersed and thermally stable metal particles were obtained with an average particle size of 1−2 nm. With the HDP method for the Pt/CNF catalysts, a linear relationship between the number of acidic oxygen-containing groups on the surface of activated CNF and the metal loading has been found. For the highest loaded catalyst, a platinum/adsorption site ratio of 0.5 was established, corresponding to about 0.7 Pt(NH3)42+ molecules/nm2. Furthermore, it has been established that with this procedure higher platinum loadings (∼4 wt %) can be achieved than with the ion adsorption procedure (<2 wt %). The HDP method using RuNO(NO3)3(H2O)2 also turned out to be suitable for the preparation of small (1−2 nm) uniform ruthenium particles on CNF with a high thermostability.