Chapters authored
Benzimidazole as Solid Electrolyte Material for Fuel Cells
This chapter is focused in the application of benzimidazole, mainly in the form of poly[2,2′-(m-phenylene)-5,5′-bisbenzimidazole] (PBI) and poly(2,5-benzimidazole) (ABPBI), in the fuel cell technology. A short introduction is given of the fuel cell principles, explaining both the theory and the high importance of this technology. PBI and ABPBI are used in a certain type of fuel cells: the polymer electrolyte fuel cells and are key materials in the composition of some of the electrolyte membranes used. Commercially available membranes composed of PBI are indicated in order to give an overview of their potential performance. The synthesis of the polymers is explained. Moreover, the preparation of the different kinds of membranes, both in proton exchange membrane fuel cells (PEMFCs) and anion exchange membrane fuel cells (AEMFCs) is studied. A deep description is given about the properties that make this family of compounds so interesting for the fuel cell technology as well as an how these polymers have been characterized with the corresponding analysis. The comparison with other ion exchange membranes is also discussed. Special attention will be given to the state of the art of different kinds of PBI/ABPBI fuel cell electrolyte membranes, in which our group and others are working nowadays.
Part of the book: Chemistry and Applications of Benzimidazole and its Derivatives
Phase Transformation Processes in the Active Material of Lead-acid Batteries
The good performance of a lead-acid battery (LAB) is defined by the good practice in the production. During this entire process, PbO and other additives will be mixed at set conditions in the massing procedure. Consequently, an active material mainly composed of unreacted PbO, lead sulfate crystals, and amorphous species will be obtained. Later, the same mass will be pasted on the grids and the curing step will be performed. In this way, the previous pasted mass will be modified and a new hard porous structure will be formed in the active material. Furthermore, this structure will be bounded to the grid through a corrosion layer. Thus, the formed plate will be conducted to the following soaking and formation procedures. In these manufacturing steps, thanks to the major role of H2SO4, the active non-conductive material will be transformed into an electrically conductive element. Therefore, the prior compounds (PbO and lead sulfate crystals) will be converted to new phases: Pb or oxidized to PbO2 on the negative and positive plate, respectively. Because of the importance of the previous phase transformations, new advanced designs are focused on the internal structure of the active material to improve the LAB performance.
Part of the book: Phase Change Materials