Self‐Assembled Polyoxometalate Supramolecular Nanosheets for Efficient and Durable Water Oxidation

Abstract Superstructures assembled from nanoscale polyoxometalates (POMs) attract considerable interest due to their well‐defined architectures and outstanding physicochemical properties. However, the targeted synthesis of self‐assembled POM‐based superstructures with high‐efficiency electrocatalytic performance remains a significant challenge. Herein, we report the rational design and construction of three POM‐based superstructures with ultrathin graphene‐like morphologies and well‐organized frameworks via a simple self‐assembled method, in which transition metals (TMs) bridge POMs into graphene‐like planes, while cetyltrimethylammonium bromide (CTAB) serves as an intercalation agent, endowing the structures with high surface area and enhanced electronic conductivity. Among the resulting materials (denote as POM‐CTAB‐TM, TM═Co, Ni, or Cu), POM‐CTAB‐Co exhibits the highest catalytic activity toward oxygen evolution reaction (OER), achieving a low overpotential of 292 mV at a current density of 10 mA cm −2 . In situ electrochemical spectroscopy and theoretical calculations underscore that the Co atoms within the POM serve as active sites and facilitate the rate‐determining step of *OOH formation. Moreover, an anion exchange membrane water electrolyzer employing POM‐CTAB‐Co as the anode and Pt/C as the cathode demonstrates exceptional performance, delivering a current density of 2 A cm −2 at a cell voltage of 2.247 V, along with remarkable durability exceeding 2000 h at an industrial‐grade current density of 500 mA cm −2 . This study develops a simple and efficient method for synthesizing supramolecular POM‐based nanosheets as OER electrocatalysts.