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

2018; Elsevier BV; Volume: 239; Linguagem: Inglês

10.1016/j.apcatb.2018.07.064

1873-3883

Haoran Yu, Nemanja Danilovic, Yang Wang, William Willis, Abhinav Poozhikunnath, Leonard J. Bonville, Chris Capuano, Katherine E. Ayers, Radenka Marić,

Electrocatalysts for Energy Conversion

• 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.