Density‐Controlled Metal Nanocluster with Modulated Surface for pH‐Universal and Robust Water Splitting

Abstract

Reducing the particle sizes of transition metals (TMs) and avoiding their aggregation are crucial for increasing the TMs atom utilization and enhancing their industrial potential. However, it is still challenging to achieve uniform distributed and density‐controlled TMs nanoclusters (NCs) under high temperatures due to the strong interatomic metallic bonds and high surface energy of NCs. Herein, a series of TMs NCs with controllable density and nitrogen‐modulated surface are prepared with the assistance of a selected covalent organic polymer (COP), which can provide continuous anchoring sites and size‐limited skeletons. The prepared Ir NCs show superior hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activities than commercial Pt/C and Ir/C in both acid and alkaline media. In particular, the as‐prepared Ir NCs exhibit remarkable full water splitting performance, reaching a current density of 10 mA cm−2 at ultralow overpotentials of 1.42 and 1.43 V in alkaline and acidic electrolyte, respectively. The excellent electrocatalytic activities are attributed to the increased surface atom utilization and the improved intrinsic activity of Ir NCs. More importantly, the Ir NCs catalyst shows superior long‐term stability due to the strong interaction between Ir NCs and the N‐doped carbon layer.

Engineering Iridium-Based Oxygen Evolution Reaction Electrocatalysts for Proton Exchange Membrane Water Electrolyzers

“…(b) HRTEM of Ir-COP at high magnification. Reproduced with permission from ref . Copyright 2023 Wiley.…”

“…51−56 Carbon-based nanoclusters (NCs) with unique physical and chemical properties, exhibit greater utilization of surface atoms than that of nanoparticles, and are less sensitive to active stability than that of SACs. 56,57 Lee and co-workers prepared a series of superuniform transition metals NCs coordinated with covalent organic polymer (COP) via condensation reactions. Taking Ir-COPs as the target sample, the synthesis mechanism and the effect of the synthesis process on particle size were explored.…”

“…Taking Ir-COPs as the target sample, the synthesis mechanism and the effect of the synthesis process on particle size were explored. 56 The particle size of Ir-COPs increased only slightly with an increase in pyrolysis temperature, implying that the migration of Ir atoms was restricted by abundant anchor sites (Figure 3a). As a result, in Figure 3b, the ultrauniform and densitycontrolled Ir NCs (about 1.52 nm) were clearly confirmed by the high-resolution transmission electron microscopy (HRTEM) of Ir-COPs.…”

“…Electrocatalysts with various morphologies have been constructed, including zero-dimensional (0D) nanoclusters/nanodots/single-atom catalysts (SACs), one-dimensional (1D) nanowires/nanotubes/nanorods, two-dimensional (2D) nanosheets, as well as three-dimensional (3D) porous structures. − Carbon-based nanoclusters (NCs) with unique physical and chemical properties, exhibit greater utilization of surface atoms than that of nanoparticles, and are less sensitive to active stability than that of SACs. , Lee and co-workers prepared a series of superuniform transition metals NCs coordinated with covalent organic polymer (COP) via condensation reactions. Taking Ir-COPs as the target sample, the synthesis mechanism and the effect of the synthesis process on particle size were explored . The particle size of Ir-COPs increased only slightly with an increase in pyrolysis temperature, implying that the migration of Ir atoms was restricted by abundant anchor sites (Figure a).…”

Defect-rich carbon-coated nickel–cobalt alloy nanoparticles enhanced the OER catalytic activity through surface reconstruction

“…18 The study shows that the full exposure of active metal sites and the acquisition of high-density dispersion 19 are important for effectively improving the catalytic activity of metal components and improving the utilization of metal atoms. A common strategy for this is to obtain small-sized metal nanoparticles 20 to improve the specific surface area. However, metal-based nanoparticles are prone to agglutination during preparation due to high surface energy, which reduces the active sites.…”