Polyelectrolytes And Proton Conductivity In Proton Exchange Membrane Fuel Cell

The global economy develops rapidly, but the environmental pollution and the energy crisis along with the economy development, which cast a shadow over the future. Currently, new energy is studied to replace oil around the world. The fuel cell is a program to solve this problem. Among them, PEM fuel cell has been researched by the scientists of USA, Japan and Germany and become the electric energy in the future because of its many advantages, such as efficient, saving energy, high working current, high specific power, high specific energy, low working temperature, using solid electrolyte membrane, avoiding electrolytic corrosion and working stability.This article introduced the three main chemical bonding methods to synthesis the polyelectrolyte. With the successfully founding of many controlled polymerization activity technology (for example, ATRP), it makes the precise control of synthesizing polyelectrolyte with different parameters of nano-level, structure, shape possible. Polyelectrolyte became the research focus, and according to the differences of atom types, functional groups, the main and the side chain, the synthetically polyelectrolyte have different functions. In this paper, we use molecular dynamics to study the influence of the quantity of the branches and the length of each branch on the star polyelectrolyte'conformation and performance, and the influence of counter ion valence on the star polyelectrolyte. So we know the adsorption capacity of star polyelectrolyte has connection with counter ion valence. In the paper we also discuss the interaction of two star polyelectrolyte, and find that the repulsive force between the star-branched polyelectrolyte has connection with the distance between them and the counter ion valence.The polyelectrolyte is dissociated into negatively charged polyelectrolyte chain and positively charged ions in solvent. And the solution can be divided into four categories:(1) Ideal solution; (2) Regular solution; (3) Non-hot solution and (4) Non-formal solution according to the mixing heat AHm and mixing entropy ASm. In order to study expediently, we assume the used polyelectrolyte solution to category 3 non-thermal solution. But in order to study the polyelectrolyte properties in solution more realistic and accurate, we should discuss the category 4 non-formal solution. First, we introduce a parameterβinto LJ potential function, then regulate the effect of solvent by changing the size of (3, and we find that asβincreases, that is, the solvent is changing from the good to poor, the star polyelectrolyte collapses continuously. We also found that the length of the Bjerrum has influence on star polyelectrolyte conformation:IncreasingλB, the stretching ability of polyelectrolyte conformation has decreased, and the bond strength of counter ion has been enhanced.In this paper we also proposed continuum-Particle coupled multi-scale algorithm. This algorithm divided system into the particle area by molecular dynamics method, the continuous area by NS equations and the coupling area between particle area and continuous area. We discussed the influence of polymer brushes grafted on the wall on the shear flow, we studied the couette shear flow and the oscillatory shear flow respectively, and finally we found the polymer brushes'damping effect to shear flow. And polymer brushes'speed variation perpendicular to shear flow direction has relationship with the form of shear flow.In this paper we also studied the Nafion proton exchange membrane which has been used most commonly in current fuel cell. We introduced the spiral structure of proton exchange membrane Nafion polymer chains in the three-dimensional space, and the cylindrical pipe from the formation of the left view. We discussed the influence of acid side chain groups'length and water content on the conduction of proton exchange membrane proton.The civil studies about the polyelectrolyte focus on the synthesizing and reviewing, the paper will fill the blank of the star polyelectrolyte concentration at home. The paper also proposes a multi-scale method to discuss the polymer brush, finally, the paper discusses the proton's conduction in the membrane from the point of proton exchange membrane's atomic structure, it provides the theoretical basis and technical support to the development and application of proton exchange membrane fuel cells, also to solving the energy crisis.