IrCo Nanoparticles Encapsulated with Carbon Nanotubes for Efficient and Stable Acidic Water Splitting

The acidic water-splitting technology based on the polymer exchange membrane can produce hydrogen efficiently, continuously, and cleanly, which is expected to alleviate the energy crisis. However, even noble metal-based electrocatalysts such as IrOx species would dissolve rapidly during acidic oxygen evolution. Herein, we successfully assemble high-density carbon nanotubes (CNTs) encapsulated with IrCo nanoparticles (NPs) on carbon cloth (IrCo@CNT/CC) using a facile MOF-templated and dicyandiamide-assisted pyrolysis strategy. Benefiting from the favorable synergistic effect between Co and Ir and the protection of CNT, the obtained IrCo@CNT/CC only requires a low cell voltage of 1.500 V to reach 10 mA cm–2 for water splitting with an extremely low Ir loading of 0.027 mg cm–2 and exhibits robust stability under continuous electrolysis for 90 h in 0.5 M H2SO4, ranking it among one of the best bifunctional electrocatalysts for acidic water splitting. Detailed experiments reveal that the CNT-encapsulated IrCo NPs in IrCo@CNT/CC remain after the hydrogen evolution reaction (HER) but transform into Co-doped IrO2 NPs after the oxygen evolution reaction (OER). Further DFT simulation calculations confirm that the Co doping in Ir and IrO2 can optimize their electronic structures to lower their energy barriers for HER and OER, respectively.