Nano-size IrOx catalyst of high activity and stability in PEM water electrolyzer with ultra-low iridium loading

• Published in: Applied catalysis. B, Environmental Environmental, 2018-12, Vol.239 (C), p.133-146
• Main Authors: Yu, Haoran, Danilovic, Nemanja, Wang, Yang, Willis, William, Poozhikunnath, Abhinav, Bonville, Leonard, Capuano, Chris, Ayers, Katherine, Maric, Radenka
• Format: Article
• Language: English
• Subjects: Anodes; Catalysis; Catalysts; Chemical synthesis; Electrochemical analysis; Electrochemistry; Electrolytes; Iridium; Iridium oxide; Load; Morphology; Nanoparticles; Organic chemistry; Oxygen evolution reaction; Oxygen evolution reactions; Proton exchange membrane water electrolysis; Protons; Reactive spray deposition technology; Sedimentation & deposition; Spray deposition; Stability; Surface charge
• ISSN: 0926-3373; 1873-3883
• DOI: 10.1016/j.apcatb.2018.07.064

[Display omitted] •Nano-size IrOx/Nafion® catalyst is synthesized with a cost-effective process.•The IrOx/Nafion® catalyst shows excellent stability of 4,500 h in MEA test.•The iridium loading is reduced to 1/30th the commercial MEA loading.•Key factors are identified for achieving high OER activity and stability. The balance of catalyst loading, activity and stability remains a challenge for the anode of proton exchange membrane (PEM) water electrolyzers. Here we report a nano-size IrOx/Nafion® composite catalyst that exhibits both outstanding activity for oxygen evolution reaction (OER) and stability in a PEM water electrolyzer. The IrOx/Nafion® catalyst layer is fabricated using a flame-based cost-effect process, reactive spray deposition technology. The IrOx/Nafion® catalyst shows >10 times improvement in OER mass activity compared to IrOx nanoparticles synthesized using the wet chemistry method. The IrOx/Nafion® catalyst also achieved ∼4,500 h of stable operation in MEA electrolyzer at 1.8 A cm−2 and 80 °C with ultra-low iridium loading of 0.08 mg cm−2. Analysis of the IrOx structure and the electrochemical performance revealed three key factors for balancing high stability and activity: (1) high ratio of Ir (IV) to Ir (III) species and high content of hydroxide on the surface; (2) high anodic charge and surface area due to nano-size IrOx particles that are well-dispersed in the Nafion® ionomer electrolyte; (3) homogeneous anode catalyst layer morphology.