Electron‐Delocalization Across High Surface Entropy Sub‐1 nm Nanobelts Toward Enhanced Electrocatalytic Urea Oxidation

Abstract Integration of inherently incompatible elements into a single sublattice, resulting in the formation of monophasic metal oxide, holds great scientific promise; it unveils that the overlooked surface entropy in subnanometer materials can thermodynamically facilitate the formation of homogeneous single‐phase structures. Here a facile approach is proposed for synthesizing multimetallic oxide subnanometer nanobelts (MMO–PMA SNBs) by harnessing the potential of phosphomolybdic acid (PMA) clusters to capture inorganic nuclei and inhibiting their subsequent growth in solvothermal reactions. Experimental and theoretical analyses show that PMA in MMO–PMA SNBs not only aids subnanometer structure formation but also induces in situ modifications to catalytic sites. The electron transfer from PMA, coupled with the loss of elemental identity of transition metals, leads to electron delocalization, jointly activating the reaction sites. The unique structure makes pentametallic oxide (PMO–PMA SNBs) achieve a current density of 10 mA cm −2 at a low potential of 1.34 V and remain stable for 24 h at 10 mA cm −2 on urea oxidation reaction (UOR). The exceptional UOR catalytic activity suggests a potential for utilizing multimetallic subnanometer nanostructures in energy conversion and environmental remediation.