2D and 3D Silica-Template-Derived MnO2 Electrocatalysts towards Enhanced Oxygen Evolution and Oxygen Reduction Activity

In this work, a hard-template-based nano-replication process is employed to prepare mesoporous MnO2 materials. We adopted four silica materials, namely, SBA-15, KIT-6, MCM-41, and MCM-48 as templates to prepare MnO2 materials by using a nanocasting route. The structural characteristics of the resultant MnO2 materials were thoroughly investigated by using XRD, BET, FESEM, HR-TEM, XPS, and Raman techniques. All studies confirmed the replication of porous MnO2 nanostructures from silica supports in beta-crystallographic form. By employing X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), we identified the existence of Mn and oxygen vacancies in the developed MnO2 material. The hydrodynamic linear sweep voltammetric technique was employed to demonstrate the efficient oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) activity of the catalyst in 0.1 M KOH solution. The KIT-6-derived MnO2 nanostructure displayed equal activity to the benchmark catalyst RuO2 . This work lays a foundation to prepare and employ ordered mesoporous MnO2 materials as OER/ORR catalysts, which have potential applications in electrochemical energy conversion and storage devices.