Cerium-Based Perovskite Mixed Metal Oxide as the Radical Scavenger for PEM Fuel Cells Operating under Low Humidity Conditions.

Abstract

When the polymer electrolyte membrane fuel cell (PEMFC) is operated under low humidity, the proton conductivity decreases due to membrane dehydration, causing adverse effects on fuel cell performance. Introducing appropriate additives to the membrane and catalyst layer to prevent membrane degradation at low humidity brings significant performance improvements to proton exchange membrane fuel cells. We developed a perovskite-structured multi-metal oxide Ce0.667Zr0.05Ti0.95O3-δ (CZTO) with high radical scavenging properties and good structural stability. The nanostructured ceramic CZTO is introduced into the membrane and cathode catalyst layer to improve the durability of the membrane electrode assembly. The Nafion-CZTO membrane exhibited maximum power densities of 1298 and 519 mW cm-2 at 100 and 20% relative humidity, respectively. The improved performance of Nafion-CZTO membranes over commercial Nafion membranes is due to the high proton conductivity and better radical scavenging properties of the CZTO additive. In addition, the expected positive effects of applying CZTO additives to the catalyst layer are verified by low charge transfer resistance and high electrochemical surface activity of the CZTO catalyst through electrochemical impedance spectroscopy and electrochemical surface area analyses.