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

A study of the lithium ion conductor Li3xLa2/3–xTiO3 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 Li0.17La0.29Ti0.54 (Li3xLa2/3–xTiO3x = 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 produce

Direct and indirest channels to molecular dissociation at metal surfaces

The influence of well-defined (100) steps on the dynamics of the dissociative chemisorption of methane, hydrogen and ammonia on Pt(533) has been investigated using molecular beam techniques and TPD spectroscopy. For CH4 on Pt(533), the enhancement in dissociation is associated with the additional direct sticking mediated by the step sites which exhibit an effective activation barrier 300meV lower than the (111) terraces. The lowest activation barrier appears for incident trajectories with an angle of ~5 - 10o compared to the surface normal. An enhanced surface temperature dependence is also observed on the Pt(533) surface over Pt(111), resulting either from the lower barrier to dissociation or the lower effective Debye temperature of the Pt atoms, as the step. H2 adsorption on Pt(533) exhibits 3 channels to dissociation, a direct channel which is the main one above 30meV, and two indirect channels. One accommodated channel which influence the sticking below 25meV and one unaccommodated channel which has a decreasing influence up to 150meV where S0(H2) stays constant at ~0.05. The unaccommodated indirect channel is not available on CO and O steps-decorated surface. The production of water from hydrogen adsorption on the O/Pt(533) is limited by the formation of hydroxyl. Ammonia adsorption is molecular at Ts &lt; 400 K and does not seem to depend strongly on the platinum surface plane, however desorption from the (100) steps of Pt(533) appears as extra shoulders on the TPD spectra. Ammonia decomposes on Pt(533) at Ts &gt; 360 K but does not on Pt(111). The dissociation of NH3 occurs in two steps: NH2 is formed and H2 produced at 400 K, then N2 and H2 both desorb at 530K.</p

The dynamics of the dissociative adsorption of methane on Pt(533)

The influence of well-defined steps on the dynamics of the dissociative chemisorption of methane on Pt(533) has been investigated using molecular beam techniques. The initial dissociative chemisorption probability S-0 has been determined as a function of incident energy E-i, angle of incidence theta(i), and surface temperature T-S. For incident kinetic energies in the range 26&lt;Ei(meV)&lt;1450, the initial dissociation probability of CH4 on the Pt(533) surface is higher than on Pt(111), for all surface temperatures investigated. This enhancement in dissociation is associated with the additional direct sticking mediated by the step sites, with no evidence for any additional indirect dynamical channel to dissociation induced by the step sites in the range of energies studied. The E-i dependence can be separated into the contributions of the (111) terraces and the (100) steps. The latter exhibits an effective activation barrier for dissociation approximate to 300 meV lower than the (111) terraces. The angular dependence can also be interpreted as having two contributions, one associated with the (111) terraces, and the second associated with the steps. The angular dependence associated with the step sites is broader than the dependence expected for the (111) terraces, and has a maximum for incident trajectories with an angle between the angles corresponding to the normal directions of the (111) and (100) facets. An enhanced T-S dependence is also observed on the Pt(533) surface over Pt(111). This is also associated with the influence of the step sites, and results either from the lower barrier to dissociation, or more likely a more effective coupling of the energy from the surface into the reaction coordinate

High-throughput synthesis and screening of ternary metal alloys for electrocatalysis

We report the application of a new method for the high-throughput synthesis and screening of thin film materials and its application to the discovery of electrocatalysts. Results are presented for the PtPdAu ternary alloy system with respect to activity for oxygen reduction. The results reveal an enhancement in activity for a range of PtPd alloy compositions over either of the pure elements. An optimum composition range of ternary alloys with significant activity was also identified. A correlation was also investigated between the surface reduction potential and the activity for oxygen reduction in both binary and ternary alloys. The results demonstrate the potential of the methodology for the discovery and optimization of electrocatalysts for a wide range of applications

Transatlantic equatorial distribution of nitrous oxide and methane

International audienc

Combinatorial electrochemical screening of fuel cell electrocatalysts

Combinatorial methods have been applied to the preparation and screening of fuel cell electrocatalysts. Hardware and software have been developed for fast sequential measurements of cyclic voltammetric and steady-state currents in 64-element half-cell arrays. The arrays were designed for the screening of high-surface-area supported electrocatalysts. Analysis software developed allowed the semiautomated processing of the large quantities of data, applying filters that defined figures of merit relevant to fuel cell catalyst activity and tolerance. Results are presented on the screening of carbon-supported platinum catalysts of varying platinum metal loading on carbon (and thus, particle size) in order to demonstrate the speed and sensitivity of the screening methodology. CO electro-oxidation, oxygen reduction, and methanol oxidation on a series of such catalysts reveal clear trends in characteristics and activities. Catalysts with smaller particle sizes reveal structure in the CO stripping voltammetry that can be associated with edge sites in addition to the closely packed planes, and this is concomitantly reduced as particle size is increased. Specific activity for steady-state methanol oxidation and oxygen reduction at room temperature in H2SO4 electrolyte is found to be a maximum for the largest particle sizes, in agreement with the literature. These trends in activity are significantly smaller than the differences in activities of promoted platinum-based alloy catalysts for the same reaction

Novel metal gates for high ? applications

The development of gate systems suitable for high ? dielectrics is critical to the advancement of complementary metal-oxide-semiconductor (CMOS) devices. Both the effective work function and material stability are key parameters to these systems. A systematic study of metal gates of the composition HfxSi1-x (0.25 ? x ? 1) is demonstrated here, including XPS, XRD and four point probe measurements. The effective work function of each material is evaluated and it is shown that it can be tuned from 4.5 to less than 4.0?eV. Suitable work functions for n-channel metal-oxide-semiconductor applications (4.05?±?0.2?eV) were achieved using hafnium rich compositions; however, XPS and diffraction measurements confirmed that these materials demonstrated a high propensity to oxidise, causing the reduction of the underlying oxides, making them unsuitable for commercial application