Ir single atoms and nanoclusters anchored on Ni aerogels for enhanced alkaline water oxidation: unravelling the Ir coordination environment and the Ir–Ni synergistic effect

Abstract

The development of efficient and durable oxygen evolution reaction (OER) catalysts is pivotal for advancing the renewable energy technologies. Herein, we report a facile two-step synthesis of Ir single atoms and sub-nanometer clusters anchored on nickel aerogels (Ir–SAs@Ni aerogel) for alkaline water oxidation. By employing ethylenediaminetetraacetic acid (EDTA) as a molecular barrier to trap and isolate Ir³⁺ ions, followed by thermal annealing under Ar/H₂, isolated Ir atoms and clusters are stabilized on conductive Ni aerogels. The resulting catalyst exhibits exceptional OER performance in 1.0 M KOH, achieving a low overpotential of 281 mV at 10 mA cm⁻², a small Tafel slope of 64.36 mV dec⁻¹, and remarkably robust stability for over 66 h, significantly outperforming the commercial IrO₂ catalyst. Multiple characterization studies reveal that the synergistic effects arise from the Ir single atoms/clusters, the strong electronic interaction between the Ir single atoms/clusters and the Ni aerogel substrate, and the porous aerogel structure which can facilitate mass/charge transfer in OER. Density function theory calculations confirm that the introduction of Ir single atoms significantly promotes the OER kinetics by lowering the key step energy barrier and optimizing the adsorption energy of the oxygen-containing intermediates. This study not only highlights the critical role of atomic-scale engineering in enhancing the catalytic activity and durability, but also offers a cost-effective strategy for designing high-performance OER catalysts toward electrochemical energy storage and conversion.