IrCo Nanoparticles Encapsulated with Carbon Nanotubes for Efficient and Stable Acidic Water Splitting
Xian Wang, Ze Qin, Jinjie Qian, Liyu Chen, Kui Shen
Abstract
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 IrO x 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 H 2 SO 4, 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 IrO 2 NPs after the oxygen evolution reaction (OER). Further DFT simulation calculations confirm that the Co doping in Ir and IrO 2 can optimize their electronic structures to lower their energy barriers for HER and OER, respectively.