Eliminating micro-porous layer from gas diffusion electrode for use in high temperature polymer electrolyte membrane fuel cell

Huaneng Su,Cordellia Sita,Qian Xu,Junjie Chong,Huaming Li,Sivakumar Pasupathi

doi:10.1016/j.jpowsour.2016.12.029

Abstract

Abstract In this work, we report a simple strategy to improve the performance of high temperature polymer electrolyte membrane fuel cell (HT-PEMFC) by eliminating the micro-porous layer (MPL) from its gas diffusion electrodes (GDEs). Due to the absence of liquid water and the general use of high amount of catalyst, the MPL in a HT-PEMFC system works limitedly. Contrarily, the elimination of the MPL leads to an interlaced micropore/macropore composited structure in the catalyst layer (CL), which favors gas transport and catalyst utilization, resulting in a greatly improved single cell performance. At the normal working voltage (0.6 V), the current density of the GDE eliminated MPL reaches 0.29 A cm−2, and a maximum power density of 0.54 W cm−2 at 0.36 V is obtained, which are comparable to the best results yet reported for the HT-PEMFCs with similar Pt loading and operated using air. Furthermore, the MPL-free GDE maintains an excellent durability during a preliminary 1400 h HT-PEMFC operation, owing to its structure advantages, indicating the feasibility of this electrode for practical applications.

Highlights

Operating polymer electrolyte membrane fuel cells (PEMFCs) at high temperature (120 oC-200 oC) can avoid some intrinsic challenges they faced at low temperature, such as complex humidification and heat management, low resistance to CO catalyst poisoning and potentially high technology costs [1].For two decades, polybenzimidazole membranes (PBI, or its derivatives) doped with phosphoric acid (PA), which can serve as proton exchange membranes for PEMFCs, have always been considered as the best candidates for high temperature operation [2]
For the first time in this work, we demonstrated the use of the gas diffusion electrodes (GDEs) eliminated micro-porous layer (MPL) for HT-PEMFC showing high performance
By inspecting the cross-section images, it is clear the conventional GDE is much thicker due to the existence of MPL whose thickness is about 4-5 times that of the CL (see Fig. 2(a)), which means the increased gas transport resistance as the gases have to diffuse across the thick MPLs to access the CLs

Summary

Introduction

Operating polymer electrolyte membrane fuel cells (PEMFCs) at high temperature (120 oC-200 oC) can avoid some intrinsic challenges they faced at low temperature, such as complex humidification and heat management, low resistance to CO catalyst poisoning and potentially high technology costs [1]. For one of the reasons it lies in the presence of PA, which impedes the transport of reactant gases from the support layers to the catalyst active sites, resulting in high mass transfer resistance, slow electrodes reaction processes [7,8]. In LT-PEMFC systems, the pores in the CLs tends to be blocked due to the presence of liquid water, which are known as water flooding and it significantly affects the cell performance due to the high mass transfer resistance resulting from it. The elimination of MPL, is economical and efficient Despite these advantages from eliminating MPL, the lack of MPL could increase the penetration of catalyst particles into the GDBL, resulting in reduced catalyst utilization. For the first time in this work, we demonstrated the use of the GDEs eliminated MPL for HT-PEMFC showing high performance

Preparation of GDEs

Physical characterization of the GDEs

Single cell test and electrochemical measurements

Structure characterization

Stability

Conclusions and remarks