(A) study on Cu-Ir nanotube catalysts for oxygen evolution reaction

Abstract

Development of highly active and durable catalysts to reduce usage of iridium for oxygen evolution reaction (OER) is essential for cost-effective hydrogen production by polymer electrolyte membrane water electrolysis. Herein, we reported Cu-Ir nanotubes (Cu-Ir NTs) with thin layer of 2 nm derived by following process, synthesis of 43 nm thickness of Cu nanowire templates, synthesis of 3.2 nm Ir shell layer on Cu core nanowire, and removing certain amount of Cu core nanowire by acid treatment. Through x-ray photoelectron spectroscopy (XPS), it was revealed that introduced Cu in Ir nanotubes change binding energy between iridium and oxygen intermediate, indicating of strong interaction between Cu and Ir. Furthermore, CO stripping revealed two times larger electrochemical surface area (ECSA) of Cu-Ir NTs (61.92 m$^2$/g) than those of Ir black (30.73 m$^2$/g). Due to copper-introduced effect and large ECSA, the Cu-Ir nanotubes exhibited outstanding OER mass activity (504 A/g) and specific activity (8.1 A/cm$^2$) than Ir black (200 A/g, 6.5 A/cm$^2$) in acid media. Also, Cu-Ir NTs showed superior durability in chronopotentiometry in current density of 10mA/cm$^2$