Performance improvement of polymer electrolyte membrane fuel cell by gas diffusion layer with atomic-layer-deposited HfO2 on microporous layer

Abstract

This study aims to enhance polymer electrolyte membrane fuel cell (PEMFC) performance in low humidity conditions without degrading the performance in high humidity conditions. The reference gas diffusion layer (GDL) is modified by deposition of HfO2 on the microporous layer (MPL) using atomic layer deposition (ALD), which was rarely used in GDL modification. Four HfO2 deposited GDLs with different numbers of deposition cycles (Hf_25, 50, 100, 200 shown in Table 1) are additionally prepared. The energy dispersive spectroscopy (EDS) image, contact angle, electrical resistance, vapor permeation rate, and liquid water saturation of the GDLs are evaluated and compared. Electrochemical performance experiments are conducted in three different humidity conditions. The results show that Hf_25 has 7% higher peak power than reference GDL due to better water management from its larger vapor permeation rate and smaller liquid water saturation. The electrochemical impedance spectroscopy (EIS) and equivalent circuit analysis demonstrate that Hf_25 has smaller charge transfer resistance and mass transport resistance in low and high humidity conditions. Hf_50, Hf_100, and Hf_200 display lower performance than Hf_25 due to increased electrical resistance and mass transport resistance, demonstrated by EIS and equivalent circuit analysis. Especially, Hf_200 shows a noticeable performance decrement than others.