Synergistic Assistance of Ir Clusters and NiCo2O4 Nanosheets Interfaces in Direct O-O Coupling for High-Efficiency Alkaline Oxygen Evolution.

Abstract

Adopting noble metals on non-noble metals is an effective strategy to balance the cost and activity of electrocatalysts. Herein, a thorough analysis of the synergistic OER is conducted at the heterogeneous interface formed by Ir clusters and NiCo2O4 based on DFT calculations. Specifically, the electrons spontaneously bring an eg occupancy of interfacial Ir close to unity after the absorbed O, providing more transferable electrons for the conversion of the absorbed O-intermediates. Besides, the diffuse distribution of electrons in the Ir 5d orbital fills the antibonding orbital after O is absorbed, avoiding the desorption difficulties caused by the stronger Ir-O bonds. The electrons transfer from Ir to Co atoms at the heterogeneous interface and fill the Co 3d band near the Fermi level, stimulating the interfacial Co to participate in the direct O-O coupling (DOOC) pathway. Experimentally, the ultrathin-modulated NiCo2O4 nanosheets are used to support Ir clusters (Ircluster-E-NiCo2O4) by the electrodeposition method. The as-synthesized Ircluster-E-NiCo2O4 catalyst achieves a current density of 10 mA cm-2 at an ultralow overpotential of 238 mV and works steadily for 100 h under a high current of 100 mA cm-2, benefiting from the efficient DOOC pathway during the OER.