Study on structural design and operational parameters to enhance the productivity of water as well as electricity in pem fuel cell

Abstract

This study focuses on the technical aspects related to the yields of water and electricity from the proton exchange membrane (PEM) fuel cell using dry or slightly humidified hydrogen streams. Useful guidelines could be developed for increasing the limiting current density (i.e., amount of drinking water from PEM fuel cell is proportional to the current density) and the amount of available drinking water from PEM fuel cells at steady state under single- and two-phase flow conditions. First, the removal of excessive liquid water accumulation in the gas flow channel and in the gas diffusion layer is important to increase the limiting current density, since excessive liquid water limits the ability of the fuel cell to increase its current density and water production. This study focuses on increasing the limiting current density by the use of design modifications to the arrangement of the micro-porous layer (MPL). The relationship between electrochemical losses and the arrangement of the MPL in PEM fuel cells was investigated by electrochemical impedance spectroscopy (EIS). The net water flux across the polymer membrane was investigated to ascertain the water transport in PEM fuel cells according to the arrangement of the MPL. The results indicated that a fuel cell with an MPL only on the cathode has an increased water flux from the cathode to the anode compared to cells with MPLs on both electrodes and cells without MPLs. Resistances to the mass transfer of oxygen are lower in cells that have an MPL on the cathode than are the resistances in the other two types of cells, which means that the molar concentration of oxygen at the reaction surface of the catalyst layer with an MPL on the cathode is higher than that of cells with MPLs on both electrodes and cells without MPLs. This indicates that the MPL forces the liquid water from the cathode side to the anode side and decreases the liquid saturation in the gas-diffusion layer at high current densities. Consequent...