Table of contents

It is well known that Pt-Ru alloy exhibits a promising catalytic activity for fuel cells. In this work we present density functional theory (DFT) study of the randomly mixed Pt-Ru alloys and discussed its stability based on the relative position of Pt and Ru atoms. The structures are modelled as five layer slabs because the ratio of surface atoms comparable with that for clusters about 3 nm sizes. The top surface fully covered by the Pt atom exhibits highest stability compared with other randomly mixed Pt-Ru alloys. We also discuss here the probability of Pt-Ru bond ratio (M_Pt-Ru/M_Pt-Ru+M_Pt-Pt) in the Pt-Ru alloy decreases with increasing the surface atom ratio (surface atom/Total number of atom), which is compared with available X-ray absorption fine structure data.

The influence of the sintering of electrocatalysts and decrease of the proton conductivity on the current-voltage performance in the HT-PEMFC was theoretically evaluated under the non-humid conditions at 150 °C, 170 °C and 190 °C. Decreasing rate of the proton conductivity was evaluated based on the tortuosity of the proton pass. The more the phosphoric acid was evaporated with a rise in temperature, the proton path found to become more tortuous and the proton conductivity was accordingly estimated to be decreased. A theoretical breakdown of the voltage drops indicated that the sintering of the electrocatalyst influenced on the voltage drop in earlier several hundreds of hours. The following voltage drop in the latter stage was caused mainly due to the decrease in the proton conductivity.

A model of transport across the ion-exchange membrane in all-vanadium redox flow batteries has been proposed based on concentrated solution theory for species with high concentration. The model is based upon the Stefan-Maxwell multicomponent diffusion equation where the fluxes of the species including protons, bisulfate, water and the sulfonate functional groups are fully coupled. The driving force for species transport has been modeled in terms of concentration and electrostatic potential gradients. The ionic transference numbers as well as water electro-osmosis drag coefficient has been calculated for different acid concentrations.

Solid oxide fuel cells (SOFCs) are blessed with high efficiency, the capability of using a variety of hydrocarbon fuels, and high impurity tolerance. Functionally graded electrodes have previously been investigated to improve SOFCs performance with controlled microstructure. However, little investigation has been focused on the cell-level optimization of power output for nonlinearly graded electrode microstructures. In this work, a multiscale electrode polarization model of SOFCs has been expanded and developed to a cell-level model. The cell-level SOFCs model has been utilized to disclose the complex relationship among the transport phenomena, which include the transports of electron, ion and gas molecules through the electrode and the electrochemical reaction at the triple phase boundaries. The work advances the understanding of the cell performance with graded microstructures. The performance of functionally graded electrodes has been analyzed to understand the effects of tailored electrode microstructures on cell power output.

We used density functional theory to study the adsorption of hydrogen, lithium, sodium, and potassium cations on different surfaces of platinum, namely the Pt(111), Pt(110), and Pt(100) surfaces. It was found that at low H⁺ concentrations alkali metal cations can compete with hydrogen for adsorption on all the studied platinum surfaces leading to a site blocking effect during the electrochemical processes involving adsorption of hydrogen in alkaline media. The strongest site blocking effect is predicted to occur on the Pt(111) surface as hydrogen and alkali metal cations adsorb in the same fcc-hollow adsorption site. On the Pt(110) and Pt(100) surface hydrogen and alkali cations adsorb on different sites and can co-exist on the surface – the most favorable adsorption site for hydrogen is a bridge site, while the hollow site is favored for all the studied alkali metal cations. Based on the calculated adsorption Gibbs free energies and the number of available adsorption sites on different surfaces, the probability of the site blocking effect by alkali cations on different surfaces of platinum was determined as Pt(111)>Pt(110)>Pt(100).

The lithium-O₂ systems capture worldwide attention as a possible battery for electric vehicle propulsion. However, there are numerous scientific and technical challenges that must be overcome if this alluring promise is to turn into reality. In this study, using first principles molecular dynamics (FPMD), we first time report the dynamical behavior of discharge deposit product such as Li₂O₂ and investigate the deposit film thickness effect on the electrical conductivity of the cathode surface. We show that how discharge products accumulate on the cathode surface with time and deposit on catalysts surface as well as influence of the species transportation process in Li-O₂ battery.

In the recent years, interest has grown in the development of anion exchange membranes (AEMs) for alkaline fuel cells, which have advantage over proton exchange membranes (PEM) fuel cells including cost and performance. In this work, we present molecular dynamics (MD) and first principles molecular dynamics (FPMD) studies to investigate transport mechanisms of OH^- using quanternized multiblock copoly(arylene ether) (QPE) and poly (phthalazinone ether sulfone keton) (PPESK) anion exchange polymers. We report here Grotthus and vehicle mechanisms for OH^- transport by molecular modeling. From our MD study for OH^- diffusion in the QPE and PPESK, diffusion properties is comparable to experimental report and OH^- transport mechanisms from FPMD simulation significantly differ with proton transport processes.