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 perovskitestructured multi-metal oxide Ce 0.667 Zr 0.05 Ti 0.95 O 3-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 -2−2 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.

Enhancing Performance and Stability of High-Temperature Proton Exchange Membranes through Multiwalled Carbon Nanotube Incorporation into Self-Cross-Linked Fluorenone-Containing Polybenzimidazole

“…High-temperature proton exchange membrane (HT-PEM) fuel cells (HT-PEMFCs), operating above 120 °C, have garnered extensive research attention due to their superior carbon monoxide (CO) tolerance and simplified hydrothermal management. − The PEM plays a pivotal role in HT-PEMFCs, employing various polymers for this purpose. ,− Notably, sulfonated polyetheretherketone, − polybenzimidazole (PBI), − sulfonated polysulfone, and poly­(vinyl alcohol) (PVA) are among the majorly studied PEMs. Phosphoric acid (PA)-doped PBI membranes stand out as a particularly promising system for HT-PEMFCs, owing to their remarkable thermal stability, PA stability, aging resistance, and modifiable polymer backbone. − The proton conductivity of PA-doped PBI membranes directly correlates with their PA content, influencing proton transport through PA hydrogen-bond networks.…”

Mn Single-Atom Tuning Fe-N-C Catalyst Enables Highly Efficient and Durable Oxygen Electrocatalysis and Zinc–Air Batteries

“…The stability decay of Fe-N-C catalysts mainly results from the oxidation of carbon substrates and poisoning of active Fe-N x . , During the ORR process, the superoxide (•HO 2 – ) and hydroxyl (•OH) radicals generated by the activation and incomplete reduction of oxygen greatly damage the Fe-N x site via oxidizing carbon to carbon dioxide or poisoning Fe–N x sites. , Thus, mitigating the attack of radicals on the Fe–N x sites is of the utmost importance in the improvement of ORR stability. − Recently, researchers have explored effective strategies to proactively scavenge radicals and, thus, balance the activity and stability of the Fe-N-C catalysts. Specifically, adding other oxide species into Fe-N-C can proactively scavenge radicals and maintain efficient ORR activity .…”