Developing highly active and durable catalysts to reduce iridium (Ir) usage for the oxygen evolution reaction (OER) is essential

for cost-effective hydrogen production via polymer electrolyte membrane water electrolysis (PEMWE). Herein, we report

copper–iridium nanotubes (Cu–Ir NTs) with an ultrathin 2 nm Ir layer for OER, synthesized through a three-step process: (1)

formation of Cu nanowire templates, (2) deposition of an Ir shell layer, and (3) partial removal of the Cu nanowire templates

via an acid treatment. X-ray photoelectron spectroscopy analysis reveals strong electronic interactions between Cu and Ir,

altering the adsorption energy of oxygen intermediates on Ir surface. Furthermore, the Cu–Ir NTs possess a high electrochemical

surface area (ECSA) of 61.9 m2/

g, nearly twice as large as Ir black (30.7 m2/

g), due to an obtained 1-dimensional

hollow structure. These synergetic effects result in outstanding OER mass activity (504 A/g) and specific activity (8.1 A/

cm2) of the Cu–Ir NTs in acidic media, significantly surpassing Ir black (200 A/g, 6.5 A/cm2). Additionally, the Cu–Ir NTs

demonstrate an extended operating time in chronopotentiometry experiment at 10 mA/cm2. These findings highlight the

potential of the Cu–Ir NTs as cost-effective and high-performance OER catalysts for PEMWE.