Patterned Design of Zif-8-Derived Microporous Layers to Enhance Pemfc Performance Over a Wide Humidity Range

Abstract

Research efforts to improve PEMFCs (proton exchange membrane fuel cells) performance are primarily focused on catalysts/electrodes and electrolytes. Often overlooked, microporous layers (MPLs) promote effective management of the water produced in PEMFCs, thus it is critical to the PEMFC performance when operating over a wide range of relative humidity (RH). Herein, Zn-based zeolitic imidazolate framework (ZIF-8)-derived material (ZDM), characterized by large cavities connected through small windows, is first introduced to construct an MPL. With promoted gas permeability, water management, and electrical conductivity, MPL equipped with a ZDM layer exhibits superior performance, surpassing commercial MPLs throughout the range of 30‒100% RH. The peak power density of an H2/air fuel cell at 70% RH utilizing a ZDM MPL achieves 1.32 W cm-2, which is 3.3 times that of commercial MPL. To further improve water management in PEMFCs, a unique patterned dual MPL is designed to boost the performance; the peak power density achieves 1.50 W cm-2 (H2/air) with a low total Pt loading of 0.3 mgPt cm–2. We demonstrate that the material and structural design of the MPL has a profoundly positive impact on the PEMFC performance.

Keywords: Microporous layers, PEMFCs, Water management, ZIF-8, Low-humidity