Low-Iridium-Content IrIn2 Intermetallics with an Unconventional Face-Centered Orthorhombic Phase for Efficient Overall Water Splitting

Iridium (Ir) is an efficient catalyst for overall water splitting, yet its widespread utilization is hampered by the substantial cost and limited stability. Alloying Ir with heteroatoms can optimize the electronic structure of the catalyst and reduce the required amount of Ir. Compared to solid solution alloys, Ir-based intermetallic compounds (IMCs) with ordered and stronger Ir-heteroatom bonds exhibit superior catalytic activity and durability. Hence, adjusting the crystal structure of Ir-based IMCs is expected to further optimize the configurations of catalytic active sites with minimal usage of Ir. Here, IrIn2 IMCs with unconventional face-centered orthorhombic structure are synthesized by a high-temperature annealing reduction method, in which the atomic percentage of Ir is only 33%. The calculation results show that the d-band center of IrIn2 is shifted upward compared to metallic Ir, resulting in enhanced adsorption with intermediates. Meanwhile, the formation of ordered IrIn bonds improves the charge transfer effectively and makes the IrIn2 IMCs resistant to atom migration and dissolution during the electrochemical reactions. For overall water splitting, the cell voltage required to achieve 10 mA cm(-2) is as low as 1.51 V under acidic condition. And IrIn2 IMCs exhibit excellent durability, with no degradation in performance >55 h.

Automated summary

Iridium-based intermetallic compounds (IMCs) with adjusted crystal structure and optimized configurations of catalytic active sites exhibit superior catalytic activity and durability in water splitting, reducing the required amount of iridium. They have important research and application value.