الفهرس 
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Abstract
Presently, fuel cells are regarded as a potential future energy source. Depending on the type, they can be used in everything from devices to large-scale power plants. As a result, fuel cells may prove to be an effective solution to the issues that arise with current power sources. Due to their potential for high energy efficiency and nearly zero pollution emissions, fuel cells are gaining popularity. They are actively researching and developing a variety of energy production technologies. A fuel cell is, by definition, an electrical cell that, unlike storage cells, can be continuously fed fuel to maintain its electrical power output indefinitely. By electrochemically reacting hydrogen and oxygen to form water, they immediately transform hydrogen or fuels containing hydrogen into electrical energy and heat.
Utilizing fuel cells has many significant benefits, but it also has many significant drawbacks. Fuel cells are prohibitively expensive in comparison to other technologies, preventing their widespread adoption. The two components that have the greatest impact on fuel cell costs are the electrode and the electrolyte. Due to its high proton conductivity, mechanical strength, and chemical stability, the Nafion membrane from DuPont Co. is the most widely used PEM for fuel cells in a variety of applications. However, the high gas permeability and instability of the Nafion membrane at high temperatures contribute to its high price. As a result, in order to overcome these drawbacks, we must find suitable Nafion membrane alternatives in this study.
Poly (vinyl alcohol) (PVA) is a polymer with a lot of interesting properties. A proton exchange membrane (PEM) was produced by utilizing two crosslinking procedures for polyvinyl alcohol (PVA): thermal crosslinking and crosslinking with sulfophthalic acid (sPTA).Firstly, the membranes were prepared using a variety of crosslinking temperatures and a constant concentration of sPTA. Additionally, the effects of the various crosslinking temperatures on the prepared membrane’s various properties were investigated. Second, the crosslinked PVA/sPTA membranes for the two series were characterized using FTIR spectroscopy, scanning electron microscopy (SEM), and wide-angle X-ray diffraction (XRD). The fabricated membranes were obtained by varying the concentration of sPTA from 5 to 30 wt.% of PVA and thermally crosslinking for one hour at a constant temperature of 100 oC. Ion exchange capacity (IEC), water uptake, methanol permeability, and proton conductivity were used to investigate the transport properties. Positron annihilation lifetime spectroscopy (PALS) was used to measure the free volume size and its distribution in the crosslinked PVA membrane.
The produced membranes displayed proton conductivity of between 8.46 and 32.7 mS/cm at various crosslinking temperatures. The cross-linking density increased as the cross-linking temperature rose, improving the produced membranes’ tensile strength and thermal stability. Using measurements from PALS (positron annihilation lifetime spectroscopy), the diameters of the membrane holes were determined. The size of the free volume hole and the membranes’ mechanical stability and methanol permeability were strongly correlated in cross-linked PVA/sPTA membranes.
IEC and proton conductivity increased with increasing sPTA concentration in the PVA membrane, but water uptake and methanol permeability decreased for various sPTA concentrations.Proton conductivity ranged from 2 to 35 mS/cm and IEC values rose to 1.6 meq/g at room temperature.The free volume content of cross-linked PVA membranes decreases when the sPTA content is increased, as evidenced by PALS data.The concentrations of nanostructure free volume defects are linked to the membrane’s transport capabilities in free volume theory, which was used to analyze and present the findings.