Mn-Based Hierarchical Polyhedral 2D/3D Nanostructures MnX₂(X = S, Se, Te) Derived from Mn-Based Metal-Organic Frameworks as High-Performance Electrocatalysts for the Oxygen Evolution Reaction

Three-dimensional (3D) nanomaterials are being explored extensively to serve as efficient electrocatalyts, which can be designed through the modification of electronic states of active sites in energy conversion applications. In this work, for the first time, a series of hierarchical polyhedral 3D nanostructures of Fe-doped manganese-based chalcogenides MnX₂(X = S, Se, Te) incorporating amorphous carbon (C) is synthesized using an Mn-based metal-organic framework as the precursor via a two-step hydrothermal route. The MnX₂/C hierarchical polyhedral nanostructures (HPNs) (X = S, Se, Te) display remarkable results such as lower overpotentials of 305, 276, and 246 mV at a current density of 10 mA cm^-2and small Tafel slopes of 85, 90, and 48 mV dec^-1, respectively. Moreover, iron-doped MnX₂(Fe-MnX₂/C-HPNs, X = S, Se, Te) display improved electrocatalytic activity, achieving lower overpotentials of 280, 246, and 210 mV at a current density of 10 mA cm^-2and smaller Tafel slopes of 85, 65, and 48 mV dec^-1, respectively. The enhanced efficiency of two-dimensional (2D)/3D hierarchical polyhedral nanostructures (Fe-MnX₂/C-HPNs, X = S, Se, Te) is due to the larger specific surface area, easy charge transport, and integrated amorphous carbon. Hence, the construction of exceptionally efficient and low-cost electrocatalysts could be facilitated by this MOF-template approach for multilayer nanostructured materials for future applications.