No abstract

This paper investigates the nano-fluidic contact angle measurement by performing molecular dynamics simulations. The contact angle between a nanowater droplet and a platinum surface is important for the design of the porous catalyst layer in low-temperature fuel cells. The measurement can generally be conducted by an atomic force microscope (AFM). However, the interaction force between the water droplet and the probe tip of the microscope may influence the measurement results. This paper employs the molecular dynamics technique to investigate the offset of the contact angle measurement. Calculations are in two sets, one simulated the water molecules clustering on the platinum surface, and the other involved the AFM measurement of the contact angle. The former case presents the original contact angle between the nano-scale water droplet and the platinum surface; the offset of the contact angle measurement due to intrusion of the AFM probe is predictable from the latter case. For engineering purposes, we present a correlation between the offset angle and the AFM measurement locations.

Methanol crossover, mainly due to diffusion mechanism, deteriorates the performance of direct methanol fuel cells. Using a molecular simulation technique, we try to reproduce the methanol diffusion event in a model Nafion membrane with an atomistic resolution. The simulation system comprises molecules of the Nafion-water-methanol-hydronium ions at four different concentrations of methanol. Molecular simulation results show that methanol molecules migrate with water clusters and hydronium ions via the sulfonic acid groups of the side chains of the electrolyte. Electro-osmotic drag coefficients and diffusion coefficients of methanol were evaluated at varied methanol concentration and compared to reported experimental results. The thermal effect on the methanol diffusion was also investigated using this molecular analysis technique.

This paper investigates how a constant magnetic field between the anode catalyst and the electrode surface affects the performance of an enzymatic biofuel cell. Molecular dynamics techniques were employed to observe the nanoscale proton transport phenomenon. The simulation model comprised a Au electrode, pyrroloquinoline quinine, flavin adenine dinucleotide, and glucose macromolecules with hydronium ions in aqueous solution. A constant magnetic field was applied parallel to the anode electrode surface in the simulation process. It is found that the magnetic field is able to enhance the hydronium mobility in the solution and the rate of the biochemical reaction increased. Simulation results show that the hydronium diffusivity increases from 3.80×10−9 m2/s to a maximum 19.91×10−9 m2/s at a glucose concentration of 27 mM and from 13.02×10−9 m2/s to a maximum 36.44×10−9 m2/s at a glucose concentration of 82 mM.

A new series of halogen-containing side chain ferroelectric liquid crystal polymers was synthesized. Mesophases were characterized by differential scanning calorimetry, polarizing optical microscopy. X-ray diffraction and molecular simulation. The behaviour of the liquid crystalline phase was investigated with variation of chiral centres. spacer units and grafted ratios. It was found that the thermal stability and temperature range of the chiral smectic C phase decreased with increasing length of the oligo-oxyethylene spacer. and decreasing mesogenic group content. The bulky substituent attached to the chiral centre reduces molecular packing in smectic liquid crystal phases, which disturbs the orientation of the side chain liquid crystal polymer. Furthermore, the influence of molecular structure on electro-optical properties of FLCPs has been studied by broad band dielectric spectroscopy (from 0.1 to 1 x 10(6) Hz)