Study of Methanol Concentration Effect in Direct Methanol Fuel Cells by Electrochemical Impedance Spectroscopy

This paper analyzes and discusses the performance of a DMFC as a function of methanol aqueous solution concentration fed at the anode, using the Electrochemical Impedance Spectroscopy (EIS). Impedance data obtained were analyzed through the development of an equivalent circuit model. Electrochemical impedance spectroscopy was used to estimate the membrane conductivity and to model the electrochemical behavior of electrodic reactions inside the fuel cell, revealing a worse overall performance by increasing methanol concentration at the anode.

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].