Christopher Edward Lee

The particle size dependence of the oxygen reduction reaction for carbon-supported platinum and palladium.

Model carbon supported Pt and Pd electrocatalysts have been prepared using a high-throughput physical vapor deposition method. For Pt, metal particle sizes are controlled between 1.5-5.5 nm over 100 electrodes of an electrochemical screening chip, allowing the oxygen reduction reaction (ORR) activity of the catalysts to be determined simultaneously. The ORR-specific current density is observed to increase with increasing particle diameter up to approximately 4 nm, at which point the activity begins to level off. The reduction in ORR activity for particles below 4 nm is accompanied by a concomitant increase in the overpotential for surface reduction. The resulting mass activity exhibits a maximum for particles with diameters of approximately 3.5 nm. These results are consistent with results published recently for high area carbon-supported Pt catalysts. For Pd particles, both the specific current density and the mass-specific activity for the ORR are observed to increase with increasing particle diameter, with no distinct optimum observed. The implications for the optimization of Pt- or Pd-based ORR catalysts for proton exchange membrane fuel cell (PEMFC) applications are discussed.

High throughput methodology for synthesis, screening, and optimization of solid state Lithium ion electrolytes

A study of the lithium ion conductor Li(3x)La(2/3-x)TiO(3) solid solution and the surrounding composition space was carried out using a high throughput physical vapor deposition system. An optimum total ionic conductivity value of 5.45 × 10(-4) S cm(-1) was obtained for the composition Li(0.17)La(0.29)Ti(0.54) (Li(3x)La(2/3-x)TiO(3)x = 0.11). This optimum value was calculated using an artificial neural network model based on the empirical data. Due to the large scale of the data set produced and the complexity of synthesis, informatics tools were required to analyze the data. Partition analysis was carried out to determine the synthetic parameters of importance and their threshold values. Multivariate curve resolution and principal component analysis were applied to the diffraction data set. This analysis enabled the construction of phase distribution diagrams, illustrating both the phases obtained and the compositional zones in which they occur. The synthetic technique presented has significant advantages over other thin film and bulk methodologies, in terms of both the compositional range covered and the nature of the materials produced.

Deposition of Ru Adatoms on Pt Using Organometallic Chemistry Electro‐oxidation of Methanol, Ethanol, 1,2‐Ethanediol, and D‐Glucose over a Surface Optimized for Oxidation of Methanol

A Pt-Ru ads surface with 10% Ru adatoms was prepared by hydrogenating Ru(COD)(η 3 -C 3 H 5 ) 2 (1, COD is 1,5-cyclooctadiene) over Pt. The onsets of stabilized potentiodynamic oxidation for several fuels ([fuel] = [H 2 SO 4 ] = 0.5 M, sweep range 0.025 to 0.60 V (vs. SHE), 5 mV s -1 , 22°C) were ethanol (∼0.2 V), methanol (∼0.3 V), and 1,2-ethanediol (∼0.45 V). The activity of D-glucose was low under these conditions. The ratio of specific current densities for potentiostatic oxidation (30 min, [fuel] = [H 2 SO 4 ] = 0.5 M, E = 0.4 V, 22°C) over Pt-Ru ads and over Pt were methanol (42) 1,2-ethanediol (4.0), ethanol (2.3), and D-glucose (1.8).