Simultaneously realizing improved activity and stability of acidic oxygen evolution reaction (OER) electrocatalysts is highly promising for developing cost-effective sustainable energy in the splitting of water technique. Herein, we report iridium nanocrystals embedded into 3D conductive clothes (Ir-NCT/CC) as a low iridium electrocatalyst realizing ultrahigh acidic OER activity and robust stability. The well-designed Ir-NCT/CC requires a low overpotential of 202 mV to reach the current density of 10 mA cm-2 with a high mass activity of 1754 A g-1. Importantly, in acidic overall water splitting, Ir-NCT/CC merely delivers a cell voltage of 1.469 V at a typical current density of 10 mA cm-2 and also maintains robust durability under continuous operation. We identify that a low working voltage drives the formation of a highly stable amorphous IrOx active phase over the surface of Ir nanocrystals (surface heterojunction IrOx/Ir-NCT) during operating conditions, which contributes to an effective and durable OER process.
