Characteristics of Pt on zeolite electrocatalyst for direct methanol fuel cell

Characteristics of Platinum (Pt) on zeolite electrocatalysts have been experimentally studied to understand its potentials for direct methanol fuel cell (DMFC) applications. The Y zeolite was chosen as a Pt-supported substrate with 1.5 wt% Pt loading on zeolite. The Pt nanoparticle size and local atomic structure in both electrochemical and gas cell treatments were investigated by using X-ray absorption spectroscopy (XAS), in particular the extended X-ray adsorption fine structure (EXAFS) method, and the electrocatalytic activity of Pt nanoparticle on Y zeolite was determined by cyclic voltammetry (CV). Studies were focused primarily on the observation of hydrogen adsorption and desorption in the hydride region, where the presence of H+ ions was critical for such a process occurred. Analyses have shown that the Pt oxides can be electrochemically reduced, due to a hydrogen ‘spillover’ phenomenon throughout zeolite structures. Based on theoretical estimation and EXAFS data fitting, it was found that the Pt nanoparticle size was 1-1.1 nm from gas cell treatment and 0.7 nm from electrochemical cell treatment. For both scenarios, the number of atoms was estimated 147 and 55 respectively, with 13 atoms at the edge of a Pt cluster for an icosahedron structure. This study demonstrated that the Pt catalytic site on zeolite can be electronically accessible; despite that zeolite is a dc insulator. The Pt/Y zeolite as a new type of electrocatalyst has shown some promises for industrial-scale fuel cell applications, such as reducing higher electrode cost and/or overcoming the difficulty of electrolyte separation

Proton modified Pt zeolite fuel cell electrocatalysts

NaY Zeolite is selected as a suitable material to host 1.5 wt% Platinum (Pt) loading on zeolite using ion exchange method (a) Pt(NH3)4(NO3)2 without excess NH4NO3 nitrate and (b) Pt(NH3)4(NO3)2 with excess NH4NO3 nitrate. The structure/reactivity relationship of Pt nanoparticle has been experimentally studied via Nafion@ bound electrodes to investigate the interaction nature of Pt with zeolite and electron transfer using the extended X-ray adsorption fine structure (EXAFS) and Pt particle was predicted at 0.7 – 1.5 (nm). Pt oxides can be electrochemically reduced via a hydrogen ‘spillover’ phenomenon. A highly dispersed small Pt particle distribution can be achieved with excessive H+ ions on zeolite acidic sites

Modelling conjugate flow and heat transfer in a ventilated room for indoor thermal comfort assessment

Conjugate natural and forced convection heat transfers in a domestic model room of finite-thickness walls and a heat source have been numerically studied. A 2-D non-ventilated square model room with a heat source is investigated at first for conditions of Prandtl number Pr=0.7 and Grashof number Gr=107. Computational results are compared with already validated numerical predictions and good agreement has been achieved in terms of stream function and temperature distributions. The study continues to consider 3-D ventilated rectangular model room with a finite-thickness wall and a heat source, in order to evaluate flow and heat transfer characteristics. Key physical features such as temperature distributions in both solid wall and indoor air domains, and heat transfer performance have been quantified, analysed and compared. These results provide the correlations among room heating device arrangement, wall thickness effect, indoor thermal comfort level and energy consumption. It was found that the arrangements of heat source and window glazing had significant impact on the temperature field, and further analysis of wall thickness and thermal conductivity variations revealed the level of the comfort temperature within the occupied zone. It was also found that for an average U-value of 0.22 W/m2K, thermal energy loss through a thinner wall of 20 cm thickness is 53% higher and indoor thermal temperature is 4.6 °C lower, compared with those of a thicker wall of 40 cm thickness. The findings would be useful for the built environment thermal engineers in design and optimisation of domestic rooms with a heat source

Numerical simulation of convective airflow in an empty room

Numerical simulation of airflow inside an empty room has been carried out for a forced convection, a natural convection and a mixed convection respectively, by using a computational fluid dynamics approach of solving the Reynolds-averaged Navier-Stokes fluid equations. Two-dimensional model was studied at first; focusing on the grid refinement, the mesh topology effect, and turbulence model influences. It was found that structured mesh results are in better agreement with available experimental measurements for all three scenarios. Further study using a three-dimensional model has shown very good agreements with test data at measuring points. Furthermore, present studies have revealed low-frequency flow unsteadiness by monitoring the time history of flow variables at measuring positions. This phenomenon has not yet reported and discussed in previous studies

Double symbolic joint entropy in nonlinear dynamic complexity analysis

Symbolizations, the base of symbolic dynamic analysis, are classified as global static and local dynamic approaches which are combined by joint entropy in our works for nonlinear dynamic complexity analysis. Two global static methods, symbolic transformations of Wessel N. symbolic entropy and base-scale entropy, and two local ones, namely symbolizations of permutation and differential entropy, constitute four double symbolic joint entropies that have accurate complexity detections in chaotic models, logistic and Henon map series. In nonlinear dynamical analysis of different kinds of heart rate variability, heartbeats of healthy young have higher complexity than those of the healthy elderly, and congestive heart failure (CHF) patients are lowest in heartbeats' joint entropy values. Each individual symbolic entropy is improved by double symbolic joint entropy among which the combination of base-scale and differential symbolizations have best complexity analysis. Test results prove that double symbolic joint entropy is feasible in nonlinear dynamic complexity analysis.Comment: 7 pages, 4 figure

The production and decay of the top partner TT in the left-right twin higgs model at the ILC and CLIC

The left-right twin Higgs model (LRTHM) predicts the existence of the top partner $T$. In this work, we make a systematic investigation for the single and pair production of this top partner $T$ through the processes: e^{+}e^{-}\to t\ov{T} + T\bar{t} and T\ov{T}, the neutral scalar (the SM-like Higgs boson $h$ or neutral pseudoscalar boson $\phi^{0}$) associate productions e^{+}e^{-}\to t\ov{T}h +T\bar{t}h, T\ov{T}h, t\ov{T}\phi^{0}+T\bar{t}\phi^{0} and T\ov{T}\phi^{0}. From the numerical evaluations for the production cross sections and relevant phenomenological analysis we find that (a) the production rates of these processes, in the reasonable parameter space, can reach the level of several or tens of fb; (b) for some cases, the peak value of the resonance production cross section can be enhanced significantly and reaches to the level of pb; (c) the subsequent decay of $T\to \phi^{+}b \to t\bar{b}b$ may generate typical phenomenological features rather different from the signals from other new physics models beyond the standard model(SM); and (d) since the relevant SM background is generally not large, some signals of the top partner $T$ predicted by the LRTHM may be detectable in the future ILC and CLIC experiments.Comment: 20pages, 15 figures and 6 Tables. Minor corrections on text. new references adde