Proton exchange membrane fuel cells (PEMFCs) are known in the state of the art as a species of fuel cell wherein an electrochemical cell converts a source of fuel into electric current. Typically, electricity is generated inside a cell system resulting from reactions between a fuel source and an oxidant taking place in an electrolytic medium.
Typical hydrogen oxygen PEMFCs comprise a membrane electrode assembly (MEA) consisting of a proton conducting polymer membrane functioning as the electrolyte which separates an anode side from a cathode side. Hydrogen is introduced on the anode side where it comes into contact with a catalyst causing dissociation of the hydrogen into constituent protons and electrons. The protons then pass through the membrane to the cathode but the electrons cannot pass through the membrane and instead traverse an external circuit, generating electricity, to the cathode to bond with the protons and form water.
A membrane electrode assembly (MEA) is the heart of the fuel cell (lyuke et al., 2003; Park et al., 2008), and consists of a sheet of proton-conducting polymer electrolyte membrane with two electrically and ionically conductive electrodes containing a platinum catalyst bonded to the opposite sides of the polymer membrane. The electric insular nature of the polymer membrane back bone and additional acid groups attached to the membrane are responsible for the ability of the membrane to prevent electrons from moving from an anode to a cathode.
Electrons produced as a result of electrochemical reactions and the general operation of single cell proton exchange membrane fuel cell (PEMFC) is presented in Equations 1-3 and FIG. 18.
FIG. 1 shows a typical membrane electrode assembly (MEA) arrangement for a single cell testing apparatus (lyuke et al., 2003)Cathode: O2+4H++4e−→2H2O  (2)Over all electrochemicalreaction: 2H2+O2→2H2O+Energy  (3)
The electrons represented in Equations 1 travel from a reaction site in the anode through the diffusion layer to the reaction site in the cathode via an external circuit. The mechanism of movement of electrons through the diffusion layer involves collision of electrons with the molecules of the diffusion layer material and releases their energy to the molecule, which results in the excitation of the diffusion layer. The excited molecule then releases an electron which collides with another molecule, thereby facilitating electron flow. The membrane does not allow electrons to flow through, but the protons produced at the anode are transported across the membrane to the reaction sites in the cathode. The transport process of the protons is facilitated by interactions of the protons with one another as well as with the water molecules (which is the by-product of the electrochemical reaction in the fuel cell) in the MEA. The acid chain in the membrane does not contribute directly to the proton transport process, but maintains the structural integrity and electronic insulation of the membrane.
The positive potential established as a result of buildup of hydrogen at the anode-membrane interface is the initial force that is required to move the protons across the membrane. While the membrane serves the purpose as stated above, the electrodes perform three functions listed below (Wilson and Gottesfeld, 1992; Haynes, 2002; Mehta and Cooper, 2002):                1. They act as physical barriers between the gaseous stream and the solid electrolyte.        2. They supply a surface site where ionization and de-ionization of fuel and oxidant may occur.        3. They provide a porous interface between ions in the gaseous streams and the ion conducting electrolyte.        
Disadvantages associated with current materials utilized as membranes in fuel cells include that they are expensive to manufacture and that the performance of the fuel cell is inadequate. The performance is influenced by various factors including the ability of the membrane to absorb water, thermal stability, porosity, solvent uptake, methanol crossover and proton conductivity.
There is a need for the development of a cost effective manufacturing process for PEMs which provides for a membrane which favourably effects at least one of the factors including: the ability of the membrane to absorb water, thermal stability, porosity, solvent uptake, methanol crossover and proton conductivity relative to the techniques comprising the current state of the art.
USPTO Backgrounds
USPTO Backgrounds