<論文・報告>流路内ガス流れ方向がPEFC性能に与える影響

Abstract

家庭用発電機や燃料電池自動車などに用いられている固体高分子形燃料電池(Polymer Electrolyte Fuel Cell : 以下PEFC)の問題点の一つとして, 水分管理が挙げられる. 本研究では, セル内の水の移動を把握するために向流, 並流, JARI-like, Anti-JARIという異なる4つのガス流路を用いてMEAの含水率分布を変え, それがセル性能に与える影響について検討した. JARI(日本自動車研究所)の規格に則ったJARI-likeと, そのH2の流れの向きを変えたものがanti-JARIである. その結果, 性能はJARI-like, Anti-JARI, 向流, 並流の順によく, 差は低電圧, 高電流域で顕著であった. また, 流れ方向によってセル内の水の挙動が異なるため, PEMとカソード触媒層の含水率分布が流路によって異なっていることが, セルの水収支の測定と数値シミュレーションにより確かめられた. セル電圧への影響は, PEMでの電位降下(抵抗過電圧)よりも反応抵抗(活性化過電圧)の方が大きかった.

One of the problems of the polymer electrolyte fuel cells (PEFCs) used in residential generators and fuel cell vehicles is water management. In this study, in order to elucidate the behavior of water in the cell, we varied the moisture content distribution in the membrane-electrode assembly (MEA) by using four different gas flow channels called countercurrent, co-current, JARI-like, and anti-JARI channels, and then we investigated the effects of the flow channel types on cell performance. The JARI-like channel is based on the standards of the Japan Automobile Research Institute (JARI), and the anti-JARI channel is the one that has the opposite flow direction of H2 gas. As a result, the performance was better in the order of the JARI-like, anti-JARI, countercurrent, and cocurrent channels, and the difference between the channel types was remarkable in the low voltage and high current regions. In addition, by measuring the net water transport through the proton exchange membrane (PEM) across the cell and carrying out numerical simulations, it was confirmed that the moisture content distribution in the PEM and that of the cathode catalyst layer depended on the four flow channel types. Of the losses from the equilibrium cell voltage, the oxygen reduction reaction resistance (activation overpotential) was greater than that of proton transport resistance in the PEM (ohmic overpotential).