Efficient and Stable Low Iridium Loaded Anodes for PEM Water Electrolysis Made Possible by Nanofiber Interlayers

Abstract

Significant reduction of the precious metal catalyst loading is one of the key challenges for the commercialization of proton-exchange membrane water electrolyzers. In this work we combine IrOx nanofibers with a conventional nanoparticle-based IrOx anode catalyst layer. With this hybrid design we can reduce the iridium loading by more than 80% while maintaining performance. In spite of an ultralow overall catalyst loading of 0.2 mgIr/cm2, a cell with a hybrid layer shows similar performance compared to a state-of-the-art cell with a catalyst loading of 1.2 mgIr/cm2 and clearly outperforms identically loaded reference cells with pure IrOx nanoparticle and pure nanofiber anodes. The improved performance is attributed to a combination of good electric contact and high porosity of the IrOx nanofibers with high surface area of the IrOx nanoparticles. Besides the improved performance, the hybrid layer also shows better stability in a potential cycling and a 150 h constant current test compared to an identically loaded nanoparticle reference.

Green ammonia as a spatial energy vector: a review

“…Like AECs, SOECs typically use common materials, the scarcest of which is yttrium; a 1 GW installation would require only about half a day's global production of this material. 118 Overall, availability of materials may inform technology selection of renewable electricity generators and electrolysis cell types; however, it should not signicantly limit the size of largescale green ammonia plant installations. It may encourage the production of ammonia in nations which have access to certain materials, or who have stable relationships with countries that produce those materials.…”

The effect of ionomer content in catalyst layers in anion-exchange membrane water electrolyzers prepared with reinforced membranes (Aemion+™)

“…16 Continuous constant operation at high current densities is a standard stress test for water electrolysis. 29 To provoke a high degradation rate, a two times higher current density was chosen in this work in comparison to the study by Fortin et al (1.0 A cm À2 vs. 0.5 A cm À2 ). In spite of this increase in current density and a three times lower anode catalyst loading employed here, we nd comparable degradation rates for the 7 wt% and 10 wt% samples of below 10 mV h À1 , which is a promising improvement of cell stability.…”

Main Hydrogen Production Processes: An Overview

“…IrOx nanofibers have been combined with a conventional nanoparticle based IrOx anodic catalyst layer, resulting in an iridium loading reduction of over 80% while maintaining the same performance. This result has been attributed to a combination among the good electrical contact and high porosity of IrOx nanofibers with the high surface area of IrOx nanoparticles [169].…”

“…In the anodic compartment, water is oxidized according to the reaction (14); the hydrated protons migrate across the membrane to reach the cathode where they are reduced ( 15 (15) In this case Ir-based oxide are usually used as catalytic anode, while unsupported or of carbon-supported Pt particles are used at the cathode [156]. Unfortunately, iridium is extremely expensive and rare, around 0.5 kg of iridium is required per megawatt installed electrolyzer power [169]. Therefore, it is crucial to obtain a significant reduction of the catalyst loading.…”