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.