Treatment of low concentration hydrogen by electrochemical pump or proton exchange membrane fuel cell
Proton exchange membrane fuel cell (PEMFC) can produce electricity through electrochemical reaction of hydrogen with oxygen with the use of a membrane and electrode assembly (MEA). In other words, the hydrogen pressure difference between the anode and cathode can produce electricity via an electrochemical process. Conversely, when we supply electricity to MEA from an external power source, we can pump up or separate hydrogen from the low-pressure anode to the high-pressure cathode, according to the principle of "concentration cell". By the way, PEMFC cannot use the fuel completely, because a cell potential decreases and electrode material may corrode when most of the fuel is consumed. Therefore the fuel released from PEMFC should be treated safely. The depleted hydrogen from PEMFC can be recovered by the electrochemical hydrogen pump, or further can be used as a fuel for the power generation by PEMFC, even though the cell voltage might be low. In this study we preliminarily measured the voltage-current characteristics of hydrogen pump and PEMFC changing the hydrogen concentration from 99.99% to 1%, as another option to platinum catalytic combustion of low concentration hydrogen. Moreover we could successfully treat the low concentration hydrogen by electrochemical pump or PEMFC, for the widely changing hydrogen concentration and mixture flow rate. The gas chromatography confirmed the hydrogen concentration of the treated gas to be 1000 ppm at most.