I. Introduction
Direct methanol fuel cells (DMFCs) are considered a very promising energy source for portable devices because they have high energy efficiency, low emissions, compact cell design, fast refueling, low temperature and pressure operation, low methanol cost and no liquid electrolyte [1]. However, the main disadvantages that prevent their use are low power density caused by the permeation of methanol through the polymer membrane and the slow electrochemical oxidation of methanol. Therefore, a better and more thorough understanding of the chemical and electrical processes that define FC behavior and reliability is needed to overcome these limitations. Fuel cells are complex systems, and their behavior depends on many variables such as current, operating temperature, pressure, methanol concentration, catalyst loading, and electrolyte characteristics [1]–[3].