Iridium-Doped Nanosized Zn–Al Layered Double Hydroxides as Efficient Water Oxidation Catalysts

• DOI: 10.1021/acsami.0c07925
• Publication Date: 2020-06-25T09:03:37Z
• Authors: Lucia Fagiolari; Marzia Bini; Ferdinando Costan...; Giordano Gatto; A. Jeremy Kropf; Fabio Marmottini; Morena Nocchetti; Evan C. Wegener; Francesco Zaccaria; Massimiliano Delf...; Riccardo Vivani; Alceo Macchioni
• Keywords: Layered double hydroxides; Nanomaterials; Noble metal

Layered double hydroxides (LDHs) are an ideal platform to host catalytic metal centers for water oxidation (WO) owing the high accessibility of interlayer region, which makes all potentially reachable and activated. Herein, we report syntheses three iridium-doped zinc–aluminum LDHs (Ir-LDHs) nanomaterials (1–3, with about 80 nm planar size a thickness 8 as derived by field emission scanning electron microscopy powder X-ray diffraction studies, respectively), carried out in confined aqueous environment reverse micelles, through very simple versatile procedure. These materials exhibit excellent performances WO driven NaIO4 at neutral pH 25 °C, iridium content low 0.5 mol % (∼0.8 wt %), leading quantitative oxygen yields (based on utilized NaIO4, turnover number up ∼10,000). Nanomaterials 1–3 display highest ever reported frequency values (up 402 min–1) any heterogeneous heterogenized catalyst, comparable only those most efficient molecular catalysts, tested under similar reaction conditions. The boost activity can be traced increased surface area pore volume (>5 times 1 order magnitude, respectively, higher than micrometric 0.3–1 μm) estimated nanosized particles, guarantee noble accessibility. absorption spectroscopy (XAS) studies suggest that nanomaterials, as-prepared after catalysis, contain mixture isolated, single octahedral Ir(III) sites, no evidence Ir–Ir scattering from second-nearest neighbors, excluding presence IrO2 nanoparticles. combination results obtained XAS, elemental analysis, ionic chromatography strongly suggests is embedded brucite-like structure LDHs, having four hydroxyls two chlorides first neighbors. demonstrate nanometric successfully exploited engineer WOCs, minimizing amount used, consistent principle noble-metal atom economy.