Papers by Author: A. Kowal

Abstract: Glassy carbon (GC) discs and platinum microcylindrical electrodes were modified with a layer of nickel(II) tetrakis 3-methoxy-4 hydroxyphenyl porphyrin (poly-TMHPP-Ni) of different loadings (Γ) between 0.6 and 10 nmol/cm2, and subsequently with a Nafion layer. The topography and in some cases the thickness of films were measured by means of contact mode AFM. SEM and optical microscopy observations were used for the comparative studies on a larger scale. The useful range of the coverage with modifying polymer was investigated. The optimal value of loading for the sensor was found to be in the range of 6-8 nmole of poly-TMHPP-Ni per cm2. We observed the Nafion layer uniformity in nanometric scale.

Abstract: Electrodes, assigned as GC/Pt-C and GC/Pt-Ru-C, were formed by deposition of Ptbased catalysts (47.5 wt % Pt + high surface area carbon) and (54 wt. % Pt-Ru alloy + high surface area carbon) on glassy carbon (GC) discs. X-ray diffraction measurements were used for the determination of the average crystallite size and phase composition of both catalysts. Crystallite size for Pt-C catalyst was 2.9 nm for Pt-fcc. In the diffraction pattern of the Pt-Ru-C catalyst two phases, e.g. Pt-Ru-fcc and Ru-hcp were refined using the Rietveld method. Crystallite sizes were 3.9 nm for Pt-Ru-fcc and 2.8 nm for Ru-hcp. STM observations of the surface of GC/Pt-C and GC/Pt-Ru-C electrodes revealed the presence of metal particles of the size in the range 2-6 nm and Pt-C or Pt- Ru-C agglomerates in the range of several tenth of nm. The thickness of the Nafion covering layer determined by AFM is ca. 100 nm. A simplified scheme of the investigated electrodes was created.

Abstract: The methanol oxidation was studied at two differently prepared supported Pt electrodes (Pt-C/GC and Pt/GC) in 0.5 M H2SO4 and 0.1 M NaOH. The supported Pt electrodes were characterized by AFM, STM TEM and HRTEM. The higher activity of Pt-C/GC than of Pt/GC catalyst, as well as negligible differences in the activities between the supported Pt catalysts and the corresponding single crystal electrodes oriented as the sites in the catalyst deposits in which Pt particles are dominant, clearly suggest the influence of the particle size effect on the catalyst activity.