A Comprehensive Review on Fuel Cells: From Fundamental Principles to PEM Fuel Cell Membranes

Fuel cells have a wide range of potential applications in various fields such as stationary power generation, transportation, and portable electronic devices, thanks to their high energy conversion efficiencies, environmentally friendly structures, and simple design features. This study takes a comprehensive approach to fuel cell technologies, starting with the fundamental operating principles and historical development process of fuel cells. Different systems, such as alkaline fuel cells (AFC), phosphoric acid fuel cells (PAFC), solid oxide fuel cells (SOFC), molten carbonate fuel cells (MCFC), proton exchange membrane fuel cells (PEMFC), and direct methanol fuel cells (DMFC), are examined and compared in detail in terms of their operating principles, advantages, limitations, and application areas. Furthermore, the theoretical performance limits of fuel cells and the losses observed in the systems are analyzed, and improvement strategies to reduce these losses are dis-cussed. Special emphasis is placed on PEMFC technology due to its high potential in automotive and portable energy sys-tems. In this context, the structural components of PEMFCs, types of proton exchange membranes, and the main character-istics expected from these membranes are comprehensively addressed. To better understand proton transfer processes, pro-ton transfer mechanisms such as Grotthuss, vehicle, and surface mechanisms are also explained in detail. In conclusion, this review aims to establish a conceptual bridge between the fundamental principles of fuel cell technologies and the current challenges and advances in PEMFC membrane development research.