Carbon Defect‐Induced Electronic Metal‐Support Interaction on Iridium Sites for Robust Water Splitting in Acidic Media

Abstract Developing efficient and robust bifunctional catalysts for acidic oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is critical for reducing the total cost and improving the large‐scale commercialization of proton exchange membrane water electrolyzer (PEMWE) technology. Herein, a composite catalyst consisted with low‐loading small Ir nanoparticles (average diameter of only 2 nm) supported on defective graphene (Ir@DG) is synthesized, which exhibits remarkable catalytic activity for both OER and HER in an acidic electrolyte, with the overpotentials of merely 297 and 27 mV to afford 10 mA cm −2 , respectively. Combined theoretical and experimental studies reveal that the strong electronic metal‐support interactions can improve the asymmetry of charge distribution on the Ir‐carbon defect interface to decrease the reaction barrier. Furthermore, the hybrid catalyst is also applied in a homemade PEMWE device to demonstrate its high performance in a practical working condition. This unique defect‐based coupling strategy provides a promising avenue to tradeoff the performance‐cost contradiction for PEMWE application.